With no end in sight to Russia's invasion of Ukraine, NATO leaders are gathering in Lithuania this week for their annual summit at a time when the world's biggest security alliance is facing new tests of its unity.

Russia's airstrike on a children's and maternity hospital in Ukraine is stirring memories of the Kremlin's past aerial campaigns waged in Chechnya and Syria.

Built and trained at a two-decade cost of $83 billion, Afghan security forces collapsed so quickly and completely — in some cases without a shot fired — that the ultimate beneficiary of the American investment turns out to be the Taliban.

As the United States ends the nearly 20-year war in Afghanistan and as the Taliban recapture much of the country, Americans are asking if the longest war in their history was worth the cost.