President Biden's decision last month to help Ukraine obtain F-16 fighter jets marked another crossing of a Russian red line that Vladimir Putin has said would transform the war and draw Washington and Moscow into direct conflict.
Despite the Russian leader's apocalyptic warnings, the United States has gradually agreed to expand Ukraine's arsenal with Javelin and Stinger missiles, HIMARS rocket launchers, advanced missile defense systems, drones, helicopters, M1 Abrams tanks and, soon, fourth-generation fighter jets.