President Biden has announced that all remaining U.S. troops will withdraw from Afghanistan by September 11, 2021 — the 20th anniversary of the 9/11 attacks that launched the war. Vox's Worldly podcast looks at what the U.S. withdrawal means for the near-term future of Afghanistan, why Biden finally made the tough call that his predecessors couldn’t (or wouldn’t), and what that decision tells us about how Biden sees the future of U.S. military engagement abroad.