The West’s defense against a Russian attack on Europe just got stronger now that Finland has joined NATO.

Ironically, you can thank Vladimir Putin’s assault on Ukraine.

The invasion, on top of his invasion of Georgia and other aggression, has left absolutely no doubt about Russia’s imperial dreams.

That pushed long-neutral Finland to seek protection: Under the terms of the NATO pact, an attack on one NATO country is an attack on all of them.

Turkey and Hungary held up Finland’s entry for months, but both relented last week, and on Tuesday, officials unfurled Finland’s flag outside the bloc’s Brussels headquarters.

Sweden’s entry, too, seems just a matter of time.

With Finland now in the mix, NATO’s border with Russia doubles to over 1,600 miles, complicating any future Russian aggression — and putting one more border state off-limits.

Finland’s contributions will also bolster the alliance’s finances and military resources. Helsinki can provide a force of as many as 280,000, counting its citizen-soldiers, as well as significant numbers of advanced tanks and artillery.

“President Putin went to war against Ukraine with the clear aim to get less NATO,” notes alliance Secretary-General Jens Stoltenberg.

“He’s getting the exact opposite.”

It’s the only rational response to Putin’s ghastly war.