Iran threatened on April 17 to close the Strait of Hormuz if the U.S. maintains its naval blockade, contradicting earlier claims the shipping route was fully reopened following a ceasefire. By Saturday, April 19, Iran followed through — its military announced closure of the strait and fired on tankers attempting transit, escalating a standoff that could disrupt roughly 20% of the world's daily oil and gas flows. The closure reverses a fragile two-week ceasefire deal reached April 8 and illustrates how the U.S. blockade and Iran's restrictions are pushing global energy markets toward crisis conditions comparable to March prices near $120/barrel. This is significant because extended closure could trigger severe global energy inflation and pressure the ceasefire toward complete collapse.