Perhaps it was the street protests in Moscow of late 2011. Perhaps it was a perception of Western perfidy in Libya earlier that year. Perhaps it was some inkling about a moment of American weakness. Perhaps it really was the ouster through a popular uprising of the grossly corrupt Yanukovych in Ukraine. Perhaps it was simply his inner K.G.B. officer rising to the surface, a yearning for the empire lost. In the end the reasons are secondary to the reality, which is that Putin has opted to ignite Russian nationalism by cultivating the myth of Western encirclement of the largest nation on earth by far. The G-7 will convene in a few days without him. Of course it will. The Russian president is no longer interested in the rules of that club. Controlled antagonism to it suits him better.

Some 15 months have gone by since the annexation of Crimea. A few things have become clear. On the whole, they are troubling. The first is how muted, really, the American reaction has been to Moscow’s seizure of a chunk of Ukrainian territory and Russia’s stirring-up of a little war in eastern Ukraine with its more than 6,000 dead. The United States is not even a party to the Minsk accords, the deeply flawed agreement to unwind the conflict that looks more like a means to freeze it in place.

Yes, there have been expressions of outrage from Washington. Yes, Secretary of State John Kerry was in Sochi last month for talks with Putin. But the bottom line is that Russian aggression has been met by a degree of American absence unthinkable even a decade ago. Follow-up talks to Minsk tend to find a Ukrainian official in a room with a Russian and two representatives of the breakaway areas of eastern Ukraine. One against three is not a credible formula for progress.

In America’s place has stood Chancellor Angela Merkel’s Germany. She speaks to Putin regularly. She has been frank in her condemnation of his actions. Without Germany, the sanctions in place against Russia would not have been effectively coordinated. But a fundamental problem remains. Postwar Germany is in essence a pacifist power. Mention of force is near anathema to the vast majority of the German people. Arming Ukraine to level the playing field (and so bolster the chances of diplomacy) is of course rejected by Merkel; it should not have been. Force is precisely what Putin has used to secure what he wanted: a truncated and dysfunctional Ukraine diverted from its Westernizing ambitions. This has been Moscow’s core victory and the core failure of Berlin and Washington.

The battle for Ukraine is going to be long. There are no quick fixes at this point. The shows of NATO resolve and presence in the Baltic, where three NATO states feel vulnerable with cause, have been important; they should be reinforced. The bolstering and reform of NATO to face Putin’s new threats is critical. There can be no relaxation of sanctions against Russia until Ukraine controls its borders once again. Through parties of the left and right — Syriza in Greece, the National Front in France — Putin is probing to weaken the European Union and the West where he can. Wobbling is not the answer.