The big security issue President Trump will have to grapple with in the new year will be the Ukraine war.

Kyiv is having manpower problems from ongoing casualties and growing draft evasion. Morale is hard to maintain with the discouraging grind of what some dub “trench warfare with drones.” Corruption scandals aren’t helping. Ukraine’s battlefield performance is astonishing, given Russia’s lethally improving drone technology and its willingness to pour often poorly trained troops into deadly assaults for usually minuscule ground gains. Kyiv’s weaponry improvisation and innovation is amazing.

But Ukraine needs much more ground and air weaponry and sufficient amounts of ammunition to go with them. Despite occasionally encouraging words, the U.S. still gives the impression it doesn’t want Kyiv to go all out in hammering key targets inside Russia.

Ukraine can still push back the Russians and thereby burst Vladimir Putin’s dream of victory. But it needs the tools to do it—in abundance.

Make no mistake, Putin’s dream of a new Russian empire still burns bright. That’s why he’s putting pressure—cyberattacks, dangerous military maneuvers, violations of airspace—on the Baltic states of Lithuania, Latvia and Estonia, which Stalin seized in 1940 and which became independent again in 1991 with the collapse of the Soviet Union. Putin also hasn’t hidden his hope of making Poland and other Central and Eastern European nations again Kremlin satellites. Those nations are being subjected to Russian provocations.

President Trump can’t wash his hands of the fundamental threat here. He must aid Ukraine unconditionally. The fate of that country will have a profound influence on the security of Europe, on how China pursues its own imperial ambitions—and on the President’s place in history.

Appeasement doesn’t win immortal peace prizes.