All my life America has been embarking on military projects it wasn't ultimately prepared to see through — Vietnam, Iraq, Afghanistan. It has sponsored or supported uprisings and rebellions and resistance movements in countries on many continents — Iran, Cuba, Chile, El Salvador, Kosovo, Libya. It has invaded, bombed, launched drone strikes and otherwise intervened in the affairs of still other countries far and wide in pursuit of sundry objectives — the Dominican Republic, Haiti, Somalia, Grenada, Panama, Syria, etc., etc.

But, of course, we are a peace-loving people. Everybody says so.

Well, OK, maybe not the Native Americans. Or the Filipinos. Or the Spanish. Or the Mexicans. Or Americans North and South who seem not to have gotten over the other side's wickedness in the Civil War. Or the British, for that matter.

Obviously, in all this I've left out reference to the "big ones," mainly because the virtue of America's violent war-making against Germany and Japan in the 20th century's two global conflicts (especially World War II) is seldom questioned.

As for the rest, suffice it to say that America has only sometimes, not always, been entirely on the side of right in its many and varied conflicts.

What's clear is that by necessity or inclination, or both, we simply are not an especially peaceful people. Neither, historically, are our European friends (need I provide a list of their wars?). We need not view Western history with a self-righteous "woke" disdain to recognize that our potential adversaries in the world might have reason to be as uneasy about our proclivities as we are about theirs.

Which brings us back to fights we may not be prepared to finish. To wit: Ukraine.

Russian President Vladimir Putin is a thug and a tyrant, of course, leading a country that's basically never been led by anything but tyrants. But, being Russian, Putin is also a man who seems to think a lot about history — and about the large, fundamental forces that shape it, like culture, religion, language and geography. Not least, geography.

If you look for Ukraine on a map of the world, you notice two interesting things: First, it's big — bigger than France; and second, it's a lot closer to Russia than to the United States.

Ukraine's capital, Kyiv, is about 5,000 miles from Washington, D.C. It's about 1,500 miles from either Paris or London. It's about 200 miles from the Russian border.

And 1,500 miles is the approximate length of that Russian frontier with Ukraine.

As British journalist Tim Marshall explains in "Prisoners of Geography: Ten Maps that Explain the World," Ukraine's landscape is largely part of the North European Plain — grasslands, or steppes, that make an excellent route for invading armies of the kind that have marched into Russia repeatedly from the West since the 1600s, including under Napoleon in 1812, under the German Kaiser in 1914 and under Adolf Hitler in 1941.

The other stubborn geographic fact Russians have been fretting about for 1,000 years or so is the vast nation's lack of a warm water port that doesn't freeze in the winter. The closest thing Russia has ever had is Sevastopol, in Crimea, a peninsula off Ukraine's Black Sea coast that Putin annexed in 2014, the last time tensions soared over Ukraine's potential realignment toward the West, the European Union and the NATO military alliance.

As if such hard practical facts weren't enough, national pride and tribal feeling are involved here. Ukraine has been part of the Russian empire on and off for many centuries. A great deal of Russian is spoken there; a great deal of Eastern Orthodox faith is proclaimed.

The point is simply that America would be well advised to notice that while Putin's imperialistic motives in Ukraine are not virtuous, they are quite likely sincere, deep and even existential. The Taliban sent America skedaddling from Afghanistan because, in the end, they simply cared a lot more about what happened there. We ultimately suffered the same problem of asymmetric commitment in Vietnam and elsewhere.

And so it is with Putin in Ukraine — plus he has a lot of divisions with which to show how much he cares.

We're assured by President Joe Biden's administration, and many who share its confidence in conventional foreign policy thinking, that the U.S. and NATO have no intention of fighting Russia over Ukraine. Our deployment of more troops and weaponry to NATO member countries in Russia's neighborhood is simply meant to send a clear signal that our commitment to defend those NATO states is unshakable.

Clear signals matter — like the signal of weakness we sent in quitting Afghanistan in disarray. What signal are we sending now when we dismiss as a "non-starter" Putin's demand that NATO rule out membership for Ukraine — membership, remember, that would obligate the Western allies to go to war against Russia if it ever came to blows with Ukraine? Could we be giving Putin a clear incentive to move against Ukraine before it joins NATO?

At the end of WWII, the Soviet Union, through the Warsaw Pact, and the West, through NATO, divided Europe into spheres of influence. The USSR's "allies" were in fact captives, of course. But since the collapse of the Soviet Union, Russia has watched every Warsaw Pact nation and several former Soviet republics attach themselves to the Western alliance, bringing it to Russia's very doorstep.

From the paranoid, history-soaked Russian point of view, which cultural/economic/political system appears to be on the march, and which looks threatened?

The world would be a better place if Putin's regime could be replaced with something better. But that might be even harder to accomplish than defeating the Taliban was.

Let's just be careful we don't start something else — something larger and more horrible — that we're not prepared to finish.

D.J. Tice is at doug.tice@startribune.com