President Biden’s leadership in the Ukraine crisis has thus far been a disaster. Before the Feb. 24 invasion, Ukraine’s president Volodymyr Zelensky implored the West to deter the attack by announcing in advance the strong sanctions it would impose in response.

Biden refused. Zelensky asked for arms. Biden sent only token amounts, excluding anti-aircraft weapons. And far from threatening a U.S. or NATO military response to an invasion, or even leaving the question in doubt, Biden repeatedly reassured Putin – right up to the day of the invasion – that the U.S. would not engage.

On the day before the invasion, Biden gave Russia the greenlight to attack

As a result, the invasion was not deterred and tens of thousands of people have been killed, millions made homeless, billions of dollars of property destroyed, and trillions of dollars of losses imposed on the world economy.

This is a catastrophe, and unless Biden’s leadership is radically improved its going to get far worse. Biden is now shipping small arms and antitank and antiaircraft missiles to Ukraine and has thus far imposed some rather serious sanctions. But these, taken together, are insufficient to prevent Ukrainian defeat. Without a serious change of course, the most likely outcome of the war will be a devastated Ukraine ruled by a totalitarian Russia, that in turn will be completely economically dependent on China.

Clearly, better leadership is necessary.

It would be futile to hold up such titans of wartime leadership as Lincoln or Churchill as examples for Biden to follow. Biden is not remotely in their intellectual class, and the situation he faces is not similar to what they had to deal with.

But there is another example of a rather ordinary man of Biden’s own party, who found himself in a comparable crisis and handled it much better. That person was Harry S. Truman, who in June 1950 suddenly found himself having to deal with the communist invasion of South Korea.

Truman’s leadership was far from perfect, but in the end, it proved adequate. In dealing with the Russian invasion of Ukraine, Biden could do a lot worse than ask himself: What would Harry do?

Like Biden, Truman failed to deter the invasion. In fact, in January 1950, his Secretary of State, Dean Acheson, gave a speech in which he defined the US national security boundary in Asia as running from Japan to the Philippines, excluding both South Korea and Taiwan.

While not as specific an invitation for invasion as Biden’s assurances to Putin, this nevertheless proved sufficient for Soviet dictator Joseph Stalin to give the green light to his puppet North Korean dictator Kim Il Sung to proceed with the attack.

Truman, as president, had done even more damage to US military capabilities than the series of post-Cold war presidents in pursuing a peace dividend through dismantling America’s conventional forces. We didn’t need a strong army anymore, said Truman’s national security team, because, in the nuclear age, large scale land warfare was a thing of the past.

As a result, in June 1950, when “the past” returned with a vengeance, the local US Army and South Korean forces found themselves with inadequate numbers, equipment, or training to deal with a North Korean blitzkrieg armed with Soviet T-34s and backed by Soviet air power.

The choices Truman faced were stark. Should he retreat or fight?

Many argued for retreat. South Korea was not a vital US interest they said, and we had no treaty commitment to defend it. Furthermore, the South Korean government was a regime of corrupt landowners and other vested interests devoted to preserving their privileges. In contrast, the equalitarian North Koreans were fighting to reunify their country. This wasn’t our fight, they said. We should just pull out. Besides, what was the alternative?

The alternative, as most Americans understood it, was total war. Realizing that refusing to fight in Korea would set a precedent of inviting communist aggression into Europe, many called for sounding the trumpet and going all-in to eliminate the Red Threat once and for all. This meant taking out not only North Korea, but its backers in communist China and the nuclear-armed Soviet Union.

Truman was not willing to go to nuclear war to save South Korea, but he was not willing to allow it to be defeated either. So he found a third alternative: limited war.

As T.R. Fehrenbach explains in his classic account of the Korean War, This Kind of War, the concept of limited war is foreign to the American mind. With the exception of the War of 1812, where we had to accept a draw after our de-facto French ally collapsed, every American war from the Revolution through World War II had been fought to total victory.

Moreover, the type of army that America celebrates, that of citizen soldiers, is ill suited to limited war overseas. Citizen soldiers, as Fehrenbach points out, only fight well when defending their homeland, as the Ukrainians are doing now, or when engaged in a crusade, as the U.S. Army was in World War II. To fight limited wars in foreign lands, you need professionals, or as Fehrenbach calls them, “legionnaires.”

The regular U.S. Army forces stationed in Korea, and their reinforcements sent from Japan, didn’t know why they were there, and rapidly retreated whenever they sensed they were being outflanked. Within weeks, all that was left of South Korea was a small enclave in the extreme southeast of the Korean peninsula around the port of Pusan. But America did have some legionnaires, in the form of its Air Force, Navy, marines, and airborne troops, and Truman allowed them to be used – but only in Korea – to decisive effect.

The first of these to go into battle were air forces based in Japan and carrier based naval air squadrons. These went in, and after engaging and shooting down many Soviet fighters, began devasting strikes on North Korean forces and supply lines. But this was not enough to turn the tide.

So, against the unanimous advice of the Joint Chiefs of Staff, Truman gave General Douglas McArthur permission to land the marines at Inchon, half-way up the Korean peninsula. As McArthur predicted, this fatally outflanked the North Korean forces pushing against the Pusan perimeter in the far south, sending them retreating in a rout.

That was followed up by American, South Korean, and allied international forces carrying the war to the banks of the Yalu River in the far north of North Korea. Then, to save their North Korean ally, the Chinese invaded en masse, driving the allies back to the 38th parallel, where the battle lines stabilized, and where they remain to this day.

Many aspects of Truman’s performance in Korea are debatable. Perhaps if he had allowed more aggressive use of American power to strike at the Chinese bases on the other side of the Yalu, the Chinese counterattack could have been forestalled, and all of Korea would be united today. Perhaps. But Truman’s goal was not to expand South Korea, but to deter communist aggression globally by showing that the U.S. would not allow it to succeed. This he did.

As a result, South Korea continued not only to exist, but to develop into a prosperous democracy, transforming itself from a Third World basket case with a per capita income less than Haiti to a cultural and technical powerhouse of 50 million people enjoying a standard of living equal to the EU average.

This brings us back to the subject of Ukraine today. Biden, like Truman, is attempting to manage a conflict with limited means, and to restrict the fighting to within the bounds of one country. But there is a key difference. Truman was not willing to accept defeat.

For Truman, failure was not an option. For Biden it is.

The Ukrainians are fighting valiantly, and their performance is exceeding all expectations. Yet they remain dangerously overmatched. While they have slowed most of the Russian advances to a crawl, the Russians are still advancing and could soon encircle and shell Kyiv, Kharkiv, Mariupol, and Odessa into oblivion.

Biden and NATO allies are now willing to send arms, but after reaching the border they must be transported inland by trucks or trains exposed to Russian air attack. Moreover, the Russian forces that have broken out of Crimea have not been contained, and are maneuvering to encircle the half of the Ukrainian army holding the line against the Russian-occupied Donbas.

There is a remedy for this. It’s the same one Truman employed without hesitation in Korea: American airpower. American fighters based in Poland and Romania could sweep Ukraine’s skies of Russian fighters, bombers, reconnaissance planes, transport planes and helicopters, rendering a crippling blow to the Russian war effort.

That done, we could bring in A-10 ground attack aircraft to make mincemeat of the Russian ground forces, including both their mobile forces in the south, their huge convoy slowly advancing on Kyiv, and their barbaric artillery currently slaughtering the civilian populations of Kharhiv and Mariupol. In short, by putting American air power together with Ukrainian resistance on the ground, we can win this war.

This is what is necessary. But the Biden administration is unwilling to do it. We can’t provide Ukraine with air cover, they say, because to do so would involve taking on Russian fighters, supposedly provoking nuclear war. So we’ll just ship the Ukrainians arms, and hope for the best. Que sera, sera. Whatever will be, will be.

However, as the example of Korea shows, engaging Russian air power with our own within a limited theater of conflict does not imply nuclear war. It didn’t in Korea because it was not in the interests of either the U.S. or USSR to go to war with each other. Nor would it have served either to expand the war by striking their adversaries’ air bases in Japan or Siberia. So what happened in Korea stayed in Korea.

The same would hold true today in Ukraine. Putin is having trouble enough taking on the Ukrainians, using all the forces at his disposal. The last thing he wants is to expand the war to bring more adversaries fully into the fight, by striking, for example, at U.S. air bases in Poland. As a result, he’ll have to accept the reality of U.S. airpower operating over Ukraine, come what may, because the alternatives for him would be worse.

If we gave Ukraine fighters now, and they used them to shoot down Russian planes, that would simply be a continuation of the current policy of supplying arms. The difference involved in having the pilots carry U.S. passports would hardly lead to world destruction.

Furthermore, Western sanctions, while insufficient to save Ukraine, are doing far more damage to Russia than would be involved in shooting down some planes. Putin has called it an act of war against Russia. Yet he has not lashed out with nukes, for the simple reason that it would make no sense to do so. If he won’t go to total war when we wreck his entire country economically, he certainly won’t for the sake of a few dozen pilots.

We can win in Ukraine, discredit Putin and open the possibility of his overthrow and the realignment of Russia with the West. Or we can allow our brothers and sisters in Ukraine to be crushed and invite further aggression, and in the process hand domination of the Eurasian continent over to China. The choice is ours.

If we allow Russia to take Ukraine, EU countries will be next.

It all comes down to this: Are we willing to do what it takes? Harry Truman was. Biden would do well to look to him for advice.

Dr. Robert Zubrin is an aerospace engineer. His latest book The Case for Space, was recently published by Prometheus books.