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We evaluated the household secondary attack rate (SAR) of the omicron and delta severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants, according to the vaccination status of the index case and household contacts; further, in vaccinated index cases, we evaluated the effect of the antibody levels on household transmission.A prospective cross-sectional study of 92 index cases and 197 quarantined household contacts was performed. Tests for SARS-CoV-2 variant type and antibody level were conducted in index cases, and results of polymerase chain reaction tests (during the quarantine period) were collected from contacts. Association of antibody levels in vaccinated index cases and SAR was evaluated by multivariate regression analysis.The SAR was higher in households exposed to omicron variant (42%) than in those exposed to delta variant (27%) (Immunisation of household members may help to mitigate the current pandemic.

Background Antibiotic resistance threatens public health worldwide, and inappropriate use of antibiotics is one of the main causes. Antibiotic use for asymptomatic bacteriuria (ABU) has been defined as “antibiotics never events”, and urinary tract infection (UTI) is one of the most common infectious diseases for which antibiotics are prescribed in Korea. To establish an effective antimicrobial stewardship strategy, a qualitative assessment of antibiotic use in actual clinical syndrome is necessary. Methods Cases of positive urine cultures (≥105 CFU/ml), performed in inpatient, outpatient, and emergency departments in April 2021 were screened in 26 hospitals located throughout Korea. Cases were classified into ABU, lower UTI, and upper UTI. The appropriateness of antibiotic use was retrospectively evaluated by infectious disease specialists using quality indicators based on the domestic clinical guideline for ABU and UTI. Figure 1.Study flow diagram Results A total of 2697 cases of ABU or UTI were included. The appropriateness of antibiotic use was assessed in 1157 cases with asymptomatic bacteriuria, 677 and 863 cases with lower and upper UTI (Figure 1). Antibiotics were prescribed in 21.7% (251 of 1157) of ABU without appropriate indication. Of 66 ABU cases with appropriate indication in which prophylactic antibiotics were prescribed, the duration of antibiotics was adequate in only 34.8% (Table 1). For lower UTI, the appropriateness of empirical and definite antibiotics was 77.8% (527 of 677) and 68.0% (353 of 519). In terms of upper UTI, 86.3% (745 of 863) and 78.2% (583 of 746) was appropriate, respectively. The duration of antibiotics was adequate in 65.7% (421 of 641) of lower UTI and 77.9% (592 of 760) in upper UTI (Table 2, 3). Conclusion This nationwide qualitative assessment of antibiotic use in ABU and UTI revealed that a significant proportion of antibiotics were prescribed inappropriately and, furthermore the duration of antibiotics was prolonged unnecessarily. Interventions for appropriate antibiotic use in ABU and UTI at the national level are required. Disclosures All Authors: No reported disclosures.

Given the limits of the prevailing hedging account for Seoul’s puzzling behavior that is in conformity with the interests of its adversary (i.e. North Korea) and potential threat (i.e. China) rather than those of its principal ally (i.e. the United States) and security cooperation partner (i.e. Japan), this article emphasizes the impact of the progressive ideology on Seoul’s security policy. In doing so, it calls for attention to a domestic source of ideology in explaining the security behaviors of a secondary state, which is under-researched and thus is poorly understood.

BACKGROUND There has been an increase in the validation of new technologies in infection control in hospital settings with an increase in demands of investigation for its role on contact tracing. OBJECTIVE This study aimed to examine the validity of a real time locating system (RTLS) versus the conventional contact tracing method in identifying high-risk contacts that lead to secondary transmission of SARS-CoV-2. METHODS A retrospective case-control study was conducted with contacts of in-hospital confirmed COVID-19 patients, who were enrolled from January 23 to March 25, 2022, at a University hospital in South Korea. Contacts were identified using either the conventional method or RTLS. The primary endpoint of this study was secondary transmission of SARS-CoV-2 among contacts. Univariate and multivariable logistic regression analysis comparing test positive contacts and negative contacts were performed. RESULTS WWhile only 74 contact cases were identified by both methods, 509 cases and 653 cases were confirmed by the conventional method and RTLS, respectively. A higher sensitivity (653/1,088, 60.0%) of the RTLS tracing method than conventional tracing method (509/1,088, 46.8%) against all methods combined was noted. The secondary attack rate in RTLS traced contacts model was 8.1%, while that of the conventional method model was 6.1%. Multivariable logistic regression model revealed that RTLS was more capable of detecting secondary transmission than the conventional method (adjusted odds ratio: 4.51, [95% confidence interval: 1.42-14.27], P=.011). CONCLUSIONS This study shows that RTLS proved beneficial when it is used as an adjunctive method to the conventional method for contact tracing that leads to secondary transmission. However, RTLS cannot completely replace traditional contact tracing.

OBJECTIVE To determine the association between insufficient sleep in the prenatal period and postpartum depression (PPD), and whether changes in sleep patterns during pregnancy increase the risk of PPD. METHODS A prospective cohort study was conducted between March 2013 and November 2017. Participants completed a sleep questionnaire pre-pregnancy and at 12, 24 and 36 gestational weeks (GW). Depressive symptoms were assessed by the Edinburgh Postnatal Depression Scale (EPDS) at 4 weeks postpartum, and the cut-off score for PPD was 10 or more. RESULTS Of 2512 participants, 410 (16.3%) were identified as having PPD. Only insufficient sleep at 36 GW was significantly associated with PPD after adjusting for confounding factors (odds ratio 1.79, 95% confidence interval 1.40-2.27, P

This article seeks to provide a theoretically compelling account for North Korea’s strategic choice to go nuclear and explores its implications for East Asian security. Its main research question is as follows: despite the obvious risks of going nuclear, what makes North Korea so desperate in its pursuit of nuclear capabilities? Contrary to the extant accounts that only emphasize either nonsecurity variables or an “external security” factor, this article conceptualizes North Korea’s security considerations as “regime survival” and explains its strategic choice from it. The central thesis of this article is that North Korea’s decision to go nuclear is a strategic choice, of which the purpose is to achieve its goals of safeguarding independence from external powers as well as ensuring regime security. North Korea pursues nuclear weapons because they not only protect Pyongyang’s regime from foreign aggressions but also help to consolidate Kim Jong-un’s domestic power. North Korea also seeks nuclear weapons in order to safeguard its independence and autonomy from China because the removal of China’s influence is critical to ensuring its regime survival in the long run. North Korea’s strategic choice to go nuclear and its emergence as a de facto nuclear power have significant implications for East Asian security.

Background Omicron variant viruses spread rapidly, even in individuals with high vaccination rates. This study aimed to determine the utility of the antibody against spike protein level as a predictor of the disease course of coronavirus disease 2019 (COVID-19) in vaccinated patients. Methods Between December 11, 2021, and February 10, 2022, we performed a prospective observational cohort study in South Korea, which included patients infected with Delta and Omicron variants. A multivariable logistic regression analysis to determine the association between antibody levels and outcomes was conducted. The relationship between antibody levels and cycle threshold (Ct) values was confirmed using a generalized linear model. Results From 106 vaccinated patients (39 Delta and 67 Omicron), the geometric mean titers of antibodies in patients with fever (≥37.5°C), hypoxia (≤94% of SpO2), pneumonia, C-reactive protein (CRP) elevation (>8 mg/L), or lymphopenia ( Conclusions Antibody levels are predictive of the clinical course of COVID-19 in vaccinated patients with Delta and Omicron variant infections. Our data highlight the need for concentrated efforts to monitor patients with severe acute respiratory syndrome coronavirus 2 infection who are at risk of low antibody levels.

Background: The treatment of zygoma complex fractures is of crucial importance in the field of plastic surgery. However, surgical methods to correct zygoma complex fractures, including the number of fixation sites, differ among operators. Although several studies have compared two-point and three-point fixation, no comparative research has yet been conducted on one-point versus two-point fixation using computed tomography scans of surgical results. Therefore, the present study aimed to address this gap in the literature by comparing surgical results between one-point and two-point fixation procedures.Methods: In this study, we randomly selected patients to undergo surgery using one of two surgical methods. We analyzed patients with unilateral zygoma complex fractures unaccompanied by other fractures according to whether they underwent one-point fixation of the zygomaticomaxillary buttress or two-point fixation of the zygomaticomaxillary buttress and the zygomaticofrontal suture. We then made measurements at three points—the zygomaticofrontal suture, inferior orbital wall, and malar height—using 3-month postoperative computed tomography images and performed statistical analyses to compare the results of the two methods.Results: All three measurements (zygomaticofrontal suture, inferior orbital wall, and malar height) showed significant differences (p < 0.05) between one-point and two-point fixation. Highly significant differences were found for the zygomaticofrontal suture and malar height parameters. The difference in the inferior wall measurements was less meaningful, even though it also reached statistical significance.Conclusion: Using three parameters in a statistical analysis of imaging findings, this study demonstrated significant differences in treatment outcomes according to the number of fixations. The results indicate that bone alignment and continuity can be achieved to a greater extent by two-point fixation instead of one-point fixation.

BackgroundOmicron variant viruses spread rapidly, even in individuals with high vaccination rates. This study aimed to determine the utility of the antibody against the spike protein level as a predictor of the disease course of COVID-19 in vaccinated patients.MethodsBetween 11 December 2021 and 10 February 2022, we performed a prospective observational cohort study in South Korea, which included patients infected with delta –and –omicron variants. Multivariable logistic regression analysis to determine the association between antibody levels and the outcomes was conducted.The relationship between antibody levels and cycle threshold (Ct) values was confirmed using a generalised linear model.ResultsFrom 106 vaccinated patients (39 delta and 67 omicron), the geometric mean titres of antibodies in patients withfever (≥37.5 °C), hypoxia (≤94% of SpO2), pneumonia, C-reactive protein (CRP) elevation (>8 mg/L), or lymphopenia (ConclusionAntibody levels are predictive of the clinical course of COVID-19 in vaccinated patients with delta and omicron variant infections. Our data highlight the need for concentrated efforts to monitor patients with SARS-CoV-2 infection who are at risk of low antibody levels.SummaryIn this prospective observation cohort study, antibody level predicts clinical course of breakthrough infection of COVID-19. Fever (aOR 0.23[0.12-0.51], hypoxia (aOR 0.23[0.08-0.7]), CRP elevation(aOR 0.52[0.29-0.0.94] and lymphopenia (aOR 0.57[0.33-0.98]) were inversely correlated with antibody levels.

North Korea’s economic and technological backwardness does not seem to allow Pyongyang to possess proficient cyberwarfare capabilities. Yet, North Korea’s cyber offensive capabilities are a major security threat in a new convergence space called the cyber–physical space (CPS) that connects the real world and the virtual world. How has North Korea become a formidable actor in the CPS, despite economic and technological disadvantages? Put differently, what makes North Korea a global cyber power despite its disconnect from international society? What are North Korea’s motivations behind strengthening its cyber capabilities in recent decades and what implications do these hold for international security? The primary objective of this article is to examine North Korea’s motivations for strengthening its cyber capabilities and analyze their implications for the sustainability of stability and peace on the Korean peninsula and beyond. By investigating the exemplary cases of North Korea’s recent cyberattacks, it seeks to explore the effective ways to manage the risks that North Korea’s enhanced cyber proficiencies pose in the current and future CPS.

We report enhanced sensing properties of Pd-coated SnO2 nanorod (NR) arrays for detecting H2 gas in N2 and dissolved in transformer oil. The Pd nanoparticles were coated on randomly ordered vertical SnO2 NR arrays by the glancing angle deposition (GLAD) method, which utilizes an electron-beam evaporator and a DC magnetron sputtering system. The Pd-coated SnO2 NR arrays exhibited high response (104 at 1% H2) in N2. Pd-coated SnO2 NR arrays were immersed and in mineral oil that contains various concentrations of dissolved H2 and the electrical response was measured. We found that the Pd-coated SnO2 NR arrays showed superior response (R = ˜96), low detection limit (0.3 ppm), and fast response times (300 s). The Pd-coated SnO2 NR arrays had a temperature coefficient of resistance (TCR) of 3.69 × 10-3 °C−1 at various oil temperatures (20–80 °C), indicating good thermal stability at high temperatures. The sensing mechanism of the Pd-coated SnO2 NR arrays was also demonstrated by using changes in the Schottky barrier height at the Pd/SnO2 interface upon exposure to H2.

Background To validate a stratification method using an inverse of treatment decision rules that can classify non-small cell lung cancer (NSCLC) patients in real-world treatment records.Methods (1) To validate the index classifier against the TNM 7th edition, we analyzed electronic health records (EHRs) of NSCLC patients diagnosed from 2011 to 2015 in a tertiary referral hospital in Seoul, Korea. Predictive accuracy, stage-specific sensitivity, specificity, positive predictive value, negative predictive value, F1 score, and c-statistic were measured.(2) To apply the index classifier in an administrative database, we analyzed NSCLC patients in Korean National Health Insurance Database, 2002-2013. Differential survival rates among the classes were examined with the log-rank test, and class-specific survival rates were compared with the reference survival rates.Results (1) In the validation study (N =1,375), the overall accuracy was 93.8% (95% CI: 92.5%-95.0%). Stage-specific c-statistic was the highest for stage I (0.97, 95% CI: 0.96-0.98) and the lowest for stage III (0.82, 95% CI: 0.77-0.87).(2) In the application study (N = 71,593), the index classifier showed a tendency for differentiating survival probabilities among classes. Compared to the reference TNM survival rates, the index classification under-estimated the survival probability for stages IA, IIIB, and IV, and over-estimated it for stages IIA and IIB.Conclusion The inverse of the treatment decision rules has a potential to supplement a routinely collected database with information encoded in the treatment decision rules to classify NSCLC patients. It requires further validation and replication in multiple clinical settings.

Background To validate a stratification method using an inverse of treatment decision rules that can classify non-small cell lung cancer (NSCLC) patients in real-world treatment records. Methods (1) To validate the index classifier against the TNM 7th edition, we analyzed electronic health records of NSCLC patients diagnosed from 2011 to 2015 in a tertiary referral hospital in Seoul, Korea. Predictive accuracy, stage-specific sensitivity, specificity, positive predictive value, negative predictive value, F1 score, and c-statistic were measured. (2) To apply the index classifier in an administrative database, we analyzed NSCLC patients in Korean National Health Insurance Database, 2002–2013. Differential survival rates among the classes were examined with the log-rank test, and class-specific survival rates were compared with the reference survival rates. Results (1) In the validation study (N = 1375), the overall accuracy was 93.8% (95% CI: 92.5–95.0%). Stage-specific c-statistic was the highest for stage I (0.97, 95% CI: 0.96–0.98) and the lowest for stage III (0.82, 95% CI: 0.77–0.87). (2) In the application study (N = 71,593), the index classifier showed a tendency for differentiating survival probabilities among classes. Compared to the reference TNM survival rates, the index classification under-estimated the survival probability for stages IA, IIIB, and IV, and over-estimated it for stages IIA and IIB. Conclusion The inverse of the treatment decision rules has a potential to supplement a routinely collected database with information encoded in the treatment decision rules to classify NSCLC patients. It requires further validation and replication in multiple clinical settings.

This cohort study examines the association between aspirin use and cholangiocarcinoma in an Asian cohort.

Purpose According to the conventional wisdom, trade is not a zero-sum game, but a positive-sum game. By allowing countries to focus on producing the goods that they can produce relatively efficiently, free trade is largely beneficial for everyone involved. Then, why are the world’s two largest economies (i.e. the USA and China) currently engaged in a trade war, which is likely to hurt their own economies? What is the driving force for the trade war between the two economic giants? The purpose of this paper is to offer an explanation of the underlying cause of the US–China trade war. Design/methodology/approach In an effort to make sense of the trade war between the USA and China, the paper draws the insights from the two international relations theories – i.e. hegemonic stability theory and power transition theory. Findings As China continues to threaten US hegemony in the world in general and East Asia in particular, the Sino–US competition for hegemony will intensify over time. As a result, the trade war between the two countries may persist longer than many anticipate. Further, even if the trade war between the two superpowers ends soon, a similar type of conflict is likely to occur later as long as the Sino–US hegemonic rivalry continues. Originality/value The central thesis of this paper is that “US fear” about its declining hegemony and China’s rapid rise as a challenger of US hegemony is driving a US-launched trade war with China. Since the underlying cause of the trade war between the world’s two largest economies is political (i.e. the Sino–US hegemonic rivalry) rather than economic (e.g. US attempts to improve the trade balance with China by imposing tariffs on Chinese goods), the paper contends that the full understanding of the trade war requires close attention to the importance of power competition between the two superpowers.

We studied the H2 sensing properties of Pd nanoparticles on vertical standing Si nanowire (NW) arrays for the detection of dissolved hydrogen (H2) gas in transformer oil. The Pd-coated Si NW arrays were fabricated by using the aqueous electroless etching method and sputtering. The Pd-coated Si NW arrays were immersed and measured in transformer oil with various dissolved concentrations of H2. We found that Pd-coated Si NW arrays showed significantly superior performance with regard to the response (∼1000%), the lowest detection limit (1 ppm), and the response time (600 s). The Pd-coated Si NW arrays showed a temperature coefficient of resistance (TCR) of 6.53 × 10−3 °C-1 at various oil temperatures (20–80 °C). Pd-coated Si NW arrays showed good reliability for the detection of H2 in oil at room temperature (20 °C), with nearly the same initial resistance for 30 days.

Many studies have found evidence that aspirin has protective effects against certain cancers, but quantitative dose–response data have been available only on a limited basis. This study aimed to confirm the dose–response relationship of aspirin usage and gastric cancer and to estimate the cumulative dose threshold of aspirin to achieve protective effects against gastric cancer in the general population. A total of 461,489 individuals in a population-based longitudinal cohort provided by the National Health Insurance Services (NHIS) in the Republic of Korea were observed from 2007 to 2012 to identify gastric cancer incident cases. The pharmacy claims data of these individuals from 2002 to 2006 were reviewed to assess cumulative medication exposure using the defined daily dose (DDD) system. Hazard ratios (HRs) of aspirin use for gastric cancer were estimated using multivariate Cox Proportional Hazard regression. Sensitivity analyses, including propensity-score matching and a nested case–control design, were performed to evaluate the variability caused by study design. A total of 5674 incident gastric cancers were identified from 2,965,500 person-years of follow-up observation, giving an overall incidence rate of 191.00 gastric cancers per 100,000 person-years. Compared to non-users, those with aspirin use of ≥3 DDD-years showed a statistically significant protective effect of aspirin use against gastric cancer; the adjusted HR (95% confidence intervals) were 0.79 (0.63–0.98) and 0.63 (0.48–0.83) for those with aspirin use of 3–4 DDD-years and 4–5 DDD-years, respectively (P for trend 3 DDD-years.

ObjectiveTo analyze literature-based data from PubMed to identify diseases and medications that have frequently been studied with major depressive disorder (MDD).Materials and methodsAbstracts of 23 799 research articles about MDD that have been published since 1948 till 2017 were analyzed using data and text mining approaches. Methods such as information extraction, frequent pattern mining, regression, and burst detection were used to explore diseases and medications that have been associated with MDD.ResultsIn addition to many mental disorders and antidepressants, we identified several nonmental health diseases and nonpsychotropic medications that have frequently been studied with MDD. Our results suggest that: (1) MDD has been studied with disorders such as Pain, Diabetes Mellitus, Wounds and Injuries, Hypertension, and Cardiovascular Diseases; (2) medications such as Hydrocortisone, Dexamethasone, Ketamine, and Lithium have been studied in terms of their side effects and off-label uses; (3) the relationships between nonmental disorders and MDD have gained increased attention from the scientific community; and (4) the bursts of Diabetes Mellitus and Cardiovascular Diseases explain the psychiatric and/or depression screening recommended by authoritative associations during the periods of the bursts.Discussion and conclusionThis study summarized and presented an overview of the previous MDD research in terms of diseases and medications that are highly relevant to MDD. The reported results can potentially facilitate hypothesis generation for future studies. The approaches proposed in the study can be used to better understand the progress and advance of the field.

We report on the H 2 sensing performance and sensing mechanism in Pd-coated n- and p- type Si nanowire (NW) arrays, which were fabricated by an aqueous electroless etching method and sputtering. We found that the resistance of the Pd-coated n -type Si NWs decreased from the base resistance, whereas that of the p- type Si NW arrays increased, upon exposure to H 2 . The sensitivity ( S = 1700% at 1% H 2 ) of Pd-coated p- type NW arrays was much greater than that of the n- type NW arrays ( S = 75%). Furthermore, we found that the dependency of the change in carrier density on H 2 concentration was significantly greater in p -type Si NW arrays, while it was negligible in the n- type NW arrays. A Schottky barrier was formed between the Pd and n- Si (ϕ M > ϕ SC ) before exposure to H 2 , which changed to an Ohmic contact (ϕ M SC ) after H 2 exposure. In contrast, an Ohmic contact was formed between the Pd and p- Si (ϕ M > ϕ SC ) before exposure to H 2 , which, after exposure, changed to a Schottky barrier (ϕ M SC ). Therefore, the p- type Si NW arrays were much more sensitive to H 2 than the n- type Si NW arrays.

Highlights • The present study analyzed the diagnosis pattern of childhood malignant diseases using public health data and viral surveillance data in Korea. • The number of newly diagnosis showed the highest monthly average in January, and the lowest in September. • Seasonal trends were apparent in acute myeloid leukemia, Non-Hodgkin’s lymphoma, acute lymphoblastic leukemia and germ cell tumors. • In winter, significantly more patients were diagnosed with acute lymphoblastic leukemia, acute myeloid leukemia, neuroblastoma, and Hodgkin’s lymphoma than in other seasons. • There was a temporal correlation with the diagnostic trends of several diseases and the prevalence of recent human parainfluenza virus., Background Several studies have reported a seasonal trend in the diagnosis of childhood cancer suggesting seasonal factors such as infection. The present study aimed to analyze the diagnosis pattern of childhood malignant diseases using public health data, and to compare this pattern with seasonal viral infection trends. Method Using the open data source of the Health Insurance Review and Assessment Service, we extracted data regarding all patients under 21 years of age and who had any cancer, aplastic anemia or myelodysplastic syndrome between September 2009 and December 2013. The positive detection rates of 11 viruses was collected from the surveillance data of Korea Centers for Disease Control and Prevention, and seasonality analysis were conducted with both data. Results In total, 9085 patients were diagnosed with malignant disease during the study period; there were about 175 new cases per month on average. Monthly stacked time series by year showed an apparent seasonal variation with the highest monthly average in January as 236, and the lowest in September as 120. In winter, significantly more patients were diagnosed with acute lymphoblastic leukemia, acute myeloid leukemia, neuroblastoma, and Hodgkin’s lymphoma than in other seasons. There was a temporal correlation with the diagnostic trends of several diseases and the prevalence of recent human parainfluenza virus. Conclusion This study tentatively suggests that the diagnosis of childhood malignancy follows a seasonal trend in Korea, and has a possible correlation with viral prevalence in several diseases. Further long-term analysis of epidemiological data is needed to explore possible causality.

This article presents an analysis of South Korea’s strategic choices over the Asian Infrastructure Investment Bank (AIIB), the Trans-Pacific Partnership (TPP), and the Terminal High Altitude Area Defense (THAAD) in light of the Sino–US competition in post-Cold War East Asia. South Korea’s puzzling behavior here represents Seoul’s hedging strategy against the uncertain future of the Sino–US competition in East Asia. The driving force of South Korea’s hedging behavior is Seoul’s dual concerns about being excessively dependent on the USA for its security at the time of China’s rapid rise on the one hand and being pulled into a growing China’s sphere of influence at the expense of traditional US–ROK security ties on the other. Reflecting Seoul’s prudent balancing acts between the two superpowers, South Korea’s hedging often results in apparently indecisive and underdetermined strategic choices in the face of the intensifying Sino–US competition. Nevertheless, South Korea’s hedging strategy allows Seoul to deepen extensive economic ties with Beijing while maintaining a traditional security alliance with Washington. The hedging behavior of South Korea, which is uniquely positioned as a strategic partner of rapidly rising China as well as a key security ally of the rebalancing USA, sheds important light on the behavior of middle powers in alliance politics, which has largely been neglected in the current literature.

The Sino–DPRK relationship had often been described, at least until the end of the Cold War, as one of “lips and teeth” or “blood-cemented” brothers. However, remarkable changes in the previously strong Sino–DPRK relations have been observed in recent years. Most importantly, the DPRK has ignored the People's Republic of China's repeated warnings to withhold nuclear tests, instead conducting them five times in a row since 2006. In response to those tests, China has vehemently criticized the DPRK. In addition, it voted for UN Security Council resolutions that imposed strict sanctions on Pyongyang. China even imposed its own sanctions against the DPRK. The strained relationship between China and North Korea is demonstrated by the fact that China's new president, Xi Jinping, has met South Korea's President Park Geun-hye eight times since he came to office in 2013, whereas he has never had a summit meeting with North Korea's new leader, Kim Jong-un, who succeeded his father, Kim Jong-il, in 2011. What has driven this dramatic change in the relationships of these two military allies? This paper argues that while multiple factors have pushed formerly strong Sino–DPRK relations into a new direction, the three most important factors are mistrust between two allies (historical), diverging interests (strategic), and growing Sino–ROK ties (economic and political).