Despite desperate please from Ukrainian President Volodymyr Zelensky and pressure from lawmakers at home, President Biden killed the Polish plan to transfer MiG-29 jets to Ukraine, fearing the deal might be viewed as an escalation of tensions by Vladimir Putin. The diplomatic blunder that began with a top European Union diplomat promising the jets to Ukraine ended when Poland suggested it would give the jets to the U.S. to deliver to Ukraine, and the U.S. said that was Poland's responsibility. Then, U.S. defense officials killed the project entirely, saying they would not support either transferring the jets themselves or backing...