BRUSSELS -- NATO is launching its largest exercise since the Cold War, rehearsing how U.S. troops could reinforce European allies in countries bordering Russia and on the alliance's eastern flank if a conflict were to flare up with a "near-peer" adversary. Some 90,000 troops are due to join the Steadfast Defender 2024 drills that will run through May, the alliance's top commander Chris Cavoli said on Thursday. But its top strategic document identifies Russia as the most significant and direct threat to NATO members' security. The last exercises of a similar size were Reforger - during the Cold War in 1988 with 125,000 participants - and Trident Juncture in 2018 with 50,000 participants, according to NATO. The troops taking part in the exercises, which will involve simulations of getting personnel to Europe as well exercises on the ground, will come from NATO countries and Sweden, which hopes to join the alliance soon.