Yet leaders are coming to Sunnylands less because of Mr Obama’s engagement than because of China and its recent assertiveness. China’s once-vaunted “smile diplomacy” in the region has seemed to turn to scowl. Its expansive claims in the South China Sea have greatly strained relations with neighbours with overlapping claims. In 2014 China dragged an oil rig into Vietnam’s territorial waters, provoking confrontations at sea and violent anti-Chinese protests on land. Chinese aggression towards the Philippines in disputed waters near the Spratly Islands emboldened the government of Benigno Aquino to ask an international tribunal in The Hague to adjudicate on the nature of China’s South China Sea claims, which are as legally vague as they are grabby. Meanwhile, ASEAN members have boosted naval co-operation and defence ties with America, Australia, Japan and India. There is even talk of tensions driving a naval arms race.