Kaja Kallas is the prime minister of Estonia.

TALLINN, Estonia — To anyone who lived under Soviet occupation, reports from Ukraine replay scenes we thought we would never see again. The bombing of civilians and the wanton destruction of buildings recall the carnage unleashed on the European continent by Hitler and Stalin. In Mariupol, a port city subjected to a brutal, horrifying siege, residents are reportedly being deported to faraway places in Russia where an uncertain fate awaits them.

My family knows what that’s like. My mother was only a 6-month-old baby when, in 1949, the Soviets deported her, together with her mother and grandmother, to Siberia. My grandfather was sent to a Siberian prison camp. They were lucky to survive and return to Estonia, but many didn’t. Today the Kremlin is reviving techniques of sheer barbarity. Those who have escaped Mariupol describe it as hell on earth.

To put an end to these horrors, the most optimistic observers have put their hope in a peace deal. But peace is not going to break out tomorrow. We must face up to the fact that the Kremlin’s idea of European and global security is completely at odds with that of the free world. And Vladimir Putin is willing to kill and repress en masse for the sake of it.

At NATO, our focus should be simple: Mr. Putin cannot win this war. He cannot even think he has won, or his appetite will grow. We need to demonstrate the will and commit resources to defend NATO territory. To check Russia’s aggression, we need to put in place a long-term policy of smart containment.

First, we must help Ukraine in every possible way. The people of Ukraine have not tired, and neither can we. True, Russia’s full-scale invasion of Ukraine has galvanized us into action. Allies and partners have made decisions with remarkable determination and unity. But now is the time to go the extra mile.

Ukrainian soldiers are able fighters, but they need weapons and matériel, including longer-range air defense assets and anti-tank missiles to better protect their skies. Defensive military aid must be our top priority, and we must commit ourselves to it for the long haul.

In Estonia, a country of 1.3 million people, we have provided Ukraine with close to $250 million worth of assistance so far. Much of that is military, but it extends to ambulances, blankets and baby food. The free world should redouble its efforts to support the people of Ukraine however possible — through the delivery of arms, food and daily essentials.

Second, we must show the aggressor that we are ready to defend ourselves and, if need be, to fight. Sometimes the best way to achieve peace is to be willing to use military strength.

To do so, we need to strengthen our collective defense, especially on the alliance’s eastern flank that borders Russia. That’s why in Estonia we are increasing the amount we spend on defense. This year, we’ll spend 2.3 percent of G.D.P.; in the coming years, that will rise to 2.5 percent. All NATO countries, irrespective of their location, should do the same: Two percent of G.D.P. must become an absolute minimum requirement. By increasing our spending individually, we can ensure we are all collectively safer.

We at NATO have a solid basis to work from. Members are committed to the defense of the whole of NATO territory, and in recent years the alliance has taken some bold, necessary steps. Among them was the establishment in 2016 of an enhanced forward presence of allied troops — multinational, combat-ready battle groups — in Poland, Lithuania, Latvia and Estonia. On Wednesday the alliance announced that it will likely double the number of battle groups on its eastern flank.

But we need to go further. The forward presence needs to become forward defense, of land, air and sea. That would mean more combat-ready allied troops stationed permanently in the Baltic States, supported by long-range artillery, air defense and other enabling capabilities. It would mean more NATO fighters in our skies ready to switch from peacetime air policing to wartime air defense. And it would mean more NATO ships patrolling the Baltic Sea.

Third, we must paralyze the Kremlin’s war machine. We must do so not only to end the bloodshed and occupation in Ukraine but also to disarm Russia economically, to prevent Mr. Putin from further expanding the war.

At the heart of the machine is oil and gas. Last year exports from hydrocarbons amounted to roughly 40 percent of the Russian state budget, and this year they’re likely to turn into the biggest source. Our focus must be on drying up these revenues. The European Union has already announced plans to cut Russian gas imports by two-thirds by the end of this year. But it can and should go further. We should also put some of the payments for Moscow’s oil and gas in a special third-party account so that the revenue does not go toward financing the war. And we should direct a significant share of these funds to a future reconstruction plan for Ukraine.

None of this will be easy or cost-free. And the time will surely come when we hear calls for the easing of sanctions. But we — NATO, the European Union and individual countries — must be patient and remain firm. There will be no business as usual with Mr. Putin’s Russia. In fact, there can be no business at all.

Fourth, we must help Ukrainians fleeing the war.

Moscow may think that forcing millions of Ukrainians to leave and seek shelter across Europe will destabilize our societies. This is also part of Mr. Putin’s war aims, and one of the tools of his hybrid warfare. We must show him he’s wrong.

Neighboring countries have already been extraordinarily welcoming in such a short period of time, and the European Union immediately gave Ukrainians the right to live and work in the bloc. In Estonia, we have welcomed many Ukrainian refugees, who now make up around 1.6 percent of our population. All countries should do as much as they can to provide a safe haven for Ukrainian refugees until they can return home.

Taken together, it’s a tall order. Stopping the Kremlin’s aggression will require time and a lot of effort. But as NATO members, Europeans and human beings, it’s a task from which we cannot flinch.

NYTimes: I’m the Prime Minister of Estonia. Putin Can’t Think He’s Won This War.

I’m the Prime Minister of Estonia. Putin Can’t Think He’s Won This War.