HIGH-STAKES BRINKMANSHIP: Just as their forces are stalemated on the battlefield, Russian President Vladimir Putin and Ukrainian President Volodymyr Zelensky are in a rhetorical standoff over preconditions for peace talks.

Putin offered to begin talks Thursday in Istanbul under the auspices of Turkey with no preconditions, while Zelensky is demanding a 30-day ceasefire, as proposed by the United States, again with no preconditions.