Will a direct military war occur between the United States and China at any point between now and December 31, 2100?

probability: 41%

rationale:

Strict criteria and exclusions. The resolution bar requires direct, sustained kinetic combat between US and PLA forces with significant casualties lasting more than a few days. Crucially, it excludes the most likely friction channels: proxy conflicts (e.g., Chinese intelligence supplied to Iran understandingwar.org), cyber and economic coercion, and isolated incidents like a single South China Sea collision. A Taiwan scenario where the US only arms Taipei without directly engaging the PLA is also excluded. This strict definition meaningfully limits the pathways to a qualifying event, keeping the probability below even odds despite the 74-year horizon. However, the casualty threshold is somewhat lower than the standard 1,000-battle-death definition of major war, as a sustained exchange lasting a week with hundreds of casualties would still qualify.

Near-term outlook and Taiwan. Taiwan remains the primary flashpoint, with the South China Sea as a secondary risk. However, near-term risks remain relatively low due to a period of managed détente and a mutual desire to avoid immediate escalation. The 2026 US intelligence community's Annual Threat Assessment explicitly states that Chinese leaders do not currently plan a 2027 invasion and have no fixed unification timeline, preferring economic and political coercion over war 3 sources. Both governments have strong incentives to avoid a devastating great-power conflict, bounded by nuclear deterrence and the catastrophic economic consequences of a clash over a global chokepoint like Taiwan reuters.com.

Long-term structural factors. Over a horizon spanning multiple leadership generations, the cumulative risk is nonetheless substantial. Historical base rates for great-power conflict in the 21st century suggest roughly a 45% chance for any major great-power war before 2100 2 sources. Because this assessment focuses on a single dyad, the baseline is somewhat lower, offset slightly by the fact that the resolution criteria demand fewer casualties than traditional definitions of major war. Assessing the risk over the century, the danger is likely front-loaded. The acute window of Taiwan vulnerability and current geopolitical tensions sustains an elevated risk through the 2050s. After 2050, the annual risk likely drops significantly due to China's severe projected demographic decline, the probable resolution or freezing of the Taiwan issue by that time, and continued mutual nuclear deterrence.

Key uncertainties. The cumulative risk could ultimately be higher if Chinese leadership decides their window for action on Taiwan is closing, if AI-enabled military competition compresses decision timelines and heightens miscalculation risk understandingwar.org, or if US alliance commitments in the South China Sea automatically escalate a localized skirmish into a broader war. Conversely, the risk could be lower if nuclear deterrence and economic interdependence prove as robust as they did during the US-Soviet Cold War, or if China's internal demographic and economic challenges substantially erode its willingness or capacity to project sustained military force later in the century. Balancing the immense time horizon against the strict resolution criteria and powerful structural deterrents justifies a 41% probability of a qualifying direct conflict.