Two countries top almost everyone's list of nations that are most important to the United States. One has been a rapidly ascendant power for more than twenty years. The other has only recently begun to recover from the collapse of its empire. One is important because of its size and fast-growing economic and military power. The other's importance is based on its impressive nuclear arsenal, huge petroleum assets, and strategic location. These countries are China and Russia.The United States pursues its relationship with both countries in a bilateral fashion. However, the status of Russia and China's relationship with one another has the ability to dramatically impact the United States' relations with both countries. For example, the Nixon-era cooperation between China and the United States occurred in part because of China's fear of war with the much stronger Soviet Union. By the late 1990s, improved Sino-Russian relations led to a common diplomatic front against a variety of U.S. interests.An Uneasy AllianceA few years later, Russia's move toward the United States after the September 11, 2001, terrorist attacks was, to some degree, encouraged by Russia's interest in hedging its bets should relations with China sour. By 2007, however, the United States' preemptive war in Iraq and American support of the color revolutions in Georgia and Ukraine deeply alarmed Russia's national security establishment, which fears further American political or military action in the former Soviet republics-territories in which Russia wishes to be the dominant foreign power. Russia has sought to counteract this trend by drawing closer to China to offset U.S. unpredictability and "meddling" in former Soviet territory, which many Russians view as their backyard.1 Nevertheless, however bold the Sino-Russian pronouncements on the need for a multipolar world may be, the countries' interaction in other areas reflects caution, if not deep-seated distrust. This wariness will continue to mitigate the intensity of Russia's cooperation with China in opposition to U.S. interests.In formulating U.S. policy toward both countries, it is indispensable to know how the Sino-Russian relationship will evolve-and why.Over the last decade, cooperation between Russia and China has increased dramatically. It now includes military sales, joint military research and development, common diplomatic positions (e.g., Chechnya, Taiwan, U.S. missile defense), nonmilitary trade, and the settlement of border issues. To a large extent, this cooperation was formally codified in the July 16, 2001, Russia-China Treaty on Good-Neighborliness and Friendly Cooperation.2As in previous treaties, (e.g., the 1689 Treaty of Nerchinsk, the 1858 Treaty of Aigun, and the 1860 Treaty of Beijing), this agreement between China and Russia was driven primarily by a mutual need for:(1) Peace on the border. As long as a Sino-American conflict over Taiwan remains a possibility, China does not want to commit the resources necessary to protect its 3,645 km (2,264 mile) border with Russia. For Russia, after the Soviet Union's collapse, Moscow had neither the money nor the desire to station large numbers of troops along its border with China; and(2) Increased trade. In the 1990s, Russia was the only country willing and able to supply China with the sophisticated military equipment and technology it coveted. Additionally, China's shortages of lumber, various ores, and petroleum products were filled through Russian production. This was fully compatible with cash-starved Russia's need to keep key industries, such as aircrafts and lumber, viable through the sale of resources and arms to China.These reasons do not completely explain the rationale for the treaty, however. According to Alexander Yakovlev, a China expert from the Russian Academy of Sciences: "Diplomats know any such treaty is always signed with a clear understanding about who is the real adversary. …