China and Russia have engaged in an increasing number of joint exercises in recent years. These drills aim to help them deter and, if necessary, defeat potential threats, such as Islamist terrorists trying to destabilize a Central Asian government, while at the same time reassuring their allies that Russia and China would protect them from such challenges. Furthermore, the exercises and other joint Russia-China military activities have a mutual reassurance function, informing Moscow and Beijing about the other's military potential and building mutual confidence about their friendly intentions toward one another. Finally, the joint exercises try to communicate to third parties, especially the United States, that Russia and China have a genuine security partnership and that it extends to cover Central Asia, a region of high priority concern for Moscow and Beijing, and possibly other areas, such as northeast Asia. Although the Sino-Russian partnership is limited in key respects, the United States should continue to monitor their defense relationship since it has the potential to become a more significant international security development.