Singapore/London/Nairobi, April 6 -- Of all the things Donald Trump has done to disrupt global commerce, from levying punitive tariffs to tearing up trade deals, few would be as consequential as withdrawing and leaving the rest of the world to secure the Persian Gulf. The move, which Trump has repeatedly threatened as his war with Iran drags on, would represent a break with decades of US policy keeping open the sea lanes that carry four-fifths of the $35 trillion global goods trade. Even the threat of reducing security for the Strait of Hormuz risks shaking confidence in a pillar of the world economy, as well as American wealth and power. Traffic through the strait has dropped to a handful of ships daily from about 135 before the war, with ...