Vladimir Putin started it. Joe Biden didn’t stop it. But, no matter his efforts to the contrary, this is the week in which Russia’s invasion of Ukraine becomes US President Donald Trump’s war. The most powerful office in the world doesn’t always invite choices. Trump is mandated to address the biggest conflict in Europe since World War II because the United States was involved, under his predecessor, as Ukraine’s key ally and sponsor. Trump could have dropped the war entirely. But instead, he chose to impose the force of his personality, initially through the idea he could end it in...