US President Donald Trump’s landmark visit to China comes as the Iran war disrupts global energy supplies, fuels economic uncertainty and adds fresh strain to Washington-Beijing ties. In the latest part of a series examining how rivalry, interdependence and geopolitical crises are reshaping the relationship between the two powers, we look at their make-or-break contest unfolding beneath the ocean surface. Last year’s military blockbuster Operation Hadal was China’s first high-budget film to...