Twin collisions in the South China Sea are testing Philippine and U.S. resolve toward Chinese gray-zone tactics in the disputed maritime region, but absent more escalatory measures, the United States remains unlikely to directly intervene militarily. On Oct. 22, two collisions took place near the Second Thomas Shoal in the South China Sea between Chinese and Philippine vessels within the latter's exclusive economic zone. First, a Chinese coast guard vessel collided with a Philippine transport ship; two hours later, a Chinese maritime militia vessel collided with a Philippine coast guard ship. Though the collisions caused no casualties, the Philippine defense secretary said during an Oct. 23 press conference that the vessels were ''intentionally hit'' and authorities are deeming it the most serious Chinese attempt yet to block the Philippines' monthly resupply mission to the shoal. The Philippines summoned the Chinese ambassador, and President Ferdinand Marcos Jr. ordered a probe to...