If Russian President Vladimir Putin isn’t about to invade Ukraine—or, more accurately, isn’t about to expand his previous invasion—he’s certainly making a good show of it.

Russian military forces have been moving into position for weeks. Russia and Belarus announced snap exercises that will continue for at least a month. President Joe Biden says he is expecting an invasion, and there are reports that the U.S. embassy in Kyiv is planning to evacuate families and nonessential personnel. Some NATO members are stepping up military aid and assistance. The British government says it has outed a Russian scheme to topple the government in Kyiv and replace it with Russian stooges (probably in the hope that exposing the plan will foil it).

If this isn’t the setup for a massive Russian invasion, it’s a damn good dress rehearsal.

Through all of this, the Biden administration has cycled through every combination of threats to deter the Russians from attacking. But the reality is this: Putin created this crisis, and only Putin can end it.

American options are limited for several reasons. Perhaps most important, no one really knows why Putin is doing this—or whether he really intends to do it at all. It is unlikely that his own inner circle even has a good read on its boss. As Fyodor Lukyanov, a well-connected Russian foreign-policy figure, put it: “The expert opinion that I can authoritatively declare is: Who the heck knows?”

Despite all the Western mythmaking about his cold cunning, Putin is emotional, volatile, and vain. His 2014 invasion, in which he seized Crimea and the eastern regions of Ukraine, was in response to the utter humiliation of seeing the Ukrainian president at the time, his ally Viktor Yanukovych, chased out of the country. When Putin moved in, no one knew when he would stop—and it is likely he didn’t either. The Russians gained real estate and inflicted pain on the Ukrainians, but without much of a plan for what to do next.