WASHINGTON—Ukraine’s weekend attacks against military airfields deep inside Russia signal the long-stalemated war is entering a perilous phase, with both sides seemingly intent on escalation and prospects for a U.

By Vladimir Soldatkin, Tom Balmforth and Huseyin HayatseverISTANBUL (Reuters) -Russia told Ukraine at peace talks on Monday that it would only agree to end the war if Kyiv gives up big new chunks of territory and accepts limits on the size of its army,

Russian and Ukrainian delegates met in Istanbul on Monday for their second set of direct peace talks, a day after Kyiv launched a shock drone attack on Russia’s nuclear-capable bombers, in an operation that President Volodymyr Zelensky said was a year and a half in the making.