The U.S. launched strikes on Iran ear­ly Tues­day, hours af­ter Pres­i­dent Don­ald Trump vowed to re­in­state an Amer­i­can block­ade of Iran­ian ports and charge ships for safe pas­sage through the Strait of Hor­muz. Iran re­spond­ed with at­tacks on Mid­dle East al­lies of the U.S.

The lat­est ex­change of fire leaves in tat­ters an in­ter­im deal meant to pause the fight­ing, re­open a wa­ter­way that is key to world en­er­gy sup­plies and give ne­go­tia­tors time to ham­mer out a per­ma­nent end to the war. In­stead, fight­ing has once again en­gulfed the re­gion, threat­ened the glob­al econ­o­my and brought warn­ings to com­mer­cial air­lines. Un­less a diplo­mat­ic so­lu­tion is found quick­ly, it could in­ten­si­fy in­to all-out war.

The fo­cus of the con­flict now is the strait, through which a fifth of all trad­ed crude oil and nat­ur­al gas passed in peace­time. Iran ef­fec­tive­ly shut the pas­sage dur­ing the war by at­tack­ing and threat­en­ing ships — a tac­tic that proved its great­est strate­gic ad­van­tage. It sent the price of oil, fer­tilis­er and oth­er goods soar­ing at a time when world lead­ers were al­ready strug­gling to ad­dress ris­ing costs.