Over a whirlwind four days of diplomacy designed to end the war in Ukraine, President Donald Trump has met with Russian President Vladimir Putin, Ukrainian President Volodymyr Zelensky, and prominent European leaders.

Trump and Zelensky engaged warmly on Monday, expressing optimism about resolving the now 3 1/2-year war, the bloodiest and largest since World War II. This represents a marked contrast from the two leaders’ disastrous White House meeting in February. Other positive signals have also come to the fore.