The Russian invasion of Ukraine resulted from two immense strategic blunders, Robert Service says. The first came on Nov. 10, when the U.S. and Ukraine signed a Charter on Strategic Partnership, which asserted America’s support for Kyiv’s right to pursue membership in the North Atlantic Treaty Organization. The pact made it likelier than ever that Ukraine would eventually join NATO—an intolerable prospect for Vladimir Putin. “It was the last straw,” Mr. Service says. Preparations immediately began for Russia’s so-called special military operation in Ukraine.