A final important factor that could make a U.S.-Chinese crisis more dangerous than those during the Cold War is geography. The focus of Cold War confrontations was primarily on land, especially in central Europe, whereas a future confrontation between China and the United States would almost certainly begin at sea. This difference would shape a U.S.-Chinese crisis in a number of ways, especially by requiring both sides to make some fateful choices early on. China’s small fleet of nuclear-armed ballistic missile submarines (SSBNs) and its much larger fleet of conventionally armed attack submarines are most secure when they remain in the shallow waters near the Chinese mainland, where poor acoustics compromise the effectiveness of U.S. undersea antisubmarine operations. Their proximity to Chinese land-based aircraft and air defenses also limits Washington’s ability to rely on its airpower and surface ships to counter them. For China’s submarine forces to play a role in a showdown with the United States, however, they would have to move out of those safer waters.

The prospect of China’s submarines breaking out would dramatically increase the instability of a crisis. Although U.S. antisubmarine warfare technology would be more effective against China’s submarines operating in less noisy open waters (where the United States also enjoys air superiority), it would not be perfect: some U.S. naval assets that came within range of surviving Chinese submarines would be at risk. Early in a crisis, therefore, the United States would be tempted to minimize this risk by sinking Chinese attack submarines as they tried to leave their home waters. Especially because there are only a few narrow routes through which Chinese submarines can reach deeper waters, the United States would be tempted to strike early rather than accept an increased risk to U.S. naval forces. Regardless of the U.S. decision, any Chinese attack submarines that managed to reach distant deeper waters would face a “use them or lose them” dilemma, thanks to their greater vulnerability to U.S. antisubmarine forces — one more potential trigger for escalation.

China’s nuclear-armed SSBNs present other risks. Under its no-first-use policy, China has clearly stated that any attack on its strategic nuclear forces would justify nuclear retaliation, making a U.S. strike against its SSBNs seem unlikely. Early in a crisis, therefore, Beijing would probably believe that it could safely deploy its SSBNs to distant, deeper waters, where they would be best positioned to execute their launch orders. Such a deep-water deployment, however, would introduce new dangers. One is the possibility that U.S. naval forces might mistake a Chinese SSBN for a conventional attack submarine and fire on it, inviting Chinese nuclear retaliation. Another is the danger that a Chinese SSBN could escalate the conflict without explicit orders from Beijing, owing to the limited communication such submarines maintain with the mainland in order to avoid detection.