NASSAU COUNTY, Aug. 15 -- The declaration came without preamble, in the middle of a Long Island rally. After defeating Iran, Donald Trump told the crowd Friday, he intends to claim the Strait of Hormuz as American territory. By evening, Tehran had a verdict for the idea: delusions.

The exchange laid bare an impasse that has defined six months of war. The Strait of Hormuz, through which roughly a fifth of the world's oil typically flows in peacetime, is already barely functioning. Two commercial vessels transited it on Friday, according to shipping trackers, against a pre-war average of 130 to 140. Whether Washington or Tehran ultimately controls the waterway may matter less, at this moment, than the fact that almost no one is using it. ...