The air forces of Australia, Japan, New Zealand, the Philippines, South Korea and the United States are flying simulated air-combat and air-to-ground missions at an American base in Guam, plus disaster-response and humanitarian-relief drills. Cope North—which started this week—has grown dramatically from its origins in 1978 as an American-Japanese exercise. This year the Philippines, spooked by Chinese assertiveness in the South China Sea, is participating for the first time, despite having a less-than-fearsome air force. The multilateral exercise is the second this week: Cobra Gold, South-East Asia’s biggest, began yesterday in Thailand. It started as a Thai-American endeavour, though America has reduced its troop levels since a junta seized power in Thailand in 2014. This year seven countries have sent soldiers; another 20 are observing, or taking part in planning or humanitarian exercises. A prudent response to China’s growing military clout, or creeping containment? It depends on where you sit.