As Western leaders struggle to respond to Vladimir Putin’s unexpectedly dramatic challenge to the post-Cold War order in Europe, the record so far is mixed. The West has assembled something approaching a united stance on the limits of the concessions it is prepared to make and on the nature of the sanctions it is willing to impose should Mr. Putin choose war. Neither hyperactive grandstanding in Paris nor phlegmatic passivity from Berlin has prevented the emergence of a common Western position. This is an accomplishment for which the Biden administration deserves credit.

Yet this is a defensive accomplishment, not a decisive one. As Mr. Putin demonstrated in his speech Monday, the Russian president is still in the driver’s seat, and it is his decisions, not ours, that will shape the next stage of the confrontation. Russia, a power that Western leaders mocked and derided for decades (“a gas station masquerading as a country,” as Sen. John McCain once put it), has seized the diplomatic and military initiative in Europe, and the West is, so far, powerless to do anything about it. We wring our hands, offer Mr. Putin off-ramps, and hope that our carefully hedged descriptions of the sanctions we are prepared to impose will change his mind.

At best, we’ve improvised a quick and dirty response to a strategic surprise, but we are very far from having a serious Russia policy and it is all too likely at this point that Mr. Putin will continue to outmaneuver his Western rivals and produce new surprises from his magician’s hat.

The West has two problems in countering Mr. Putin. The first is a problem of will. The West does not want a confrontation with Russia and in any crisis the goal remains to calm things down. That basic approach not only makes appeasement an attractive option whenever difficulties appear; it prevents us from thinking proactively. When Russia stops bothering us, we stop thinking about Russia.

The second is a problem of imagination. Western leaders still do not understand Mr. Putin. Most of them see that he is not just another colorless timeserver who thinks that appointing a record number of female economists to the board of his central bank constitutes a historic accomplishment. They are beginning to see that he is in quest of bigger game and that he means what he says about reassembling the Soviet Union and reviving Russian power. But they have not yet really fathomed the gulf between Mr. Putin’s world and their own—and until they do, he will continue to confound their expectations and disrupt their agendas.