Afghanistan’s rapid unraveling is already raising grumblings about the credibility of the U.S., compounding the wounds of the Donald Trump years and reinforcing the idea that America’s backing for its allies is not unlimited.

The Taliban’s lightning advance comes at a moment when many in Europe and Asia had hoped that President Joe Biden would re-establish America’s firm presence in international affairs, especially as China and Russia angle to extend their influence. Now America’s retreat is bound to sow doubts.

"When Biden says, ‘America is back,’ many people will say, ‘Yes, America is back home,’” said François Heisbourg, a French defense analyst.