Wars have unintended consequences. They rarely turn out the way the experts tell us they will. Just ask the officials who provided rosy scenarios for the wars in Vietnam, Afghanistan and Iraq, only to be proven horribly wrong. Just ask the mothers of the soldiers who were killed or wounded in action during those wars. Just ask the millions of civilians who became “collateral damage”.

That is why we must do everything possible to try and find a diplomatic solution to what could be an enormously destructive war in Ukraine.

No one knows exactly what the human costs of such a war would be. But there are estimates that there could be over 50,000 civilian casualties in Ukraine, and millions of refugees flooding neighboring countries as they flee what could be the worst European conflict since the second world war. In addition, of course, there would be many thousands of deaths within the Ukrainian and Russian militaries. There is also the possibility that this “regional” war could escalate to other parts of Europe. What might happen then is even more horrifying.

But that’s not all. The sanctions against Russia and Russia’s threatened response to those sanctions, could result in massive economic upheaval – with impacts on energy, banking, food and the day-to-day needs of ordinary people throughout the entire world. It is likely that Russians will not be the only people suffering from sanctions. And, by the way, any hope of international cooperation to address the existential threat of global climate crisis and future pandemics would suffer a major setback.

We should be clear about who is most responsible for this looming crisis: Vladimir Putin. Having already seized parts of Ukraine in 2014, the Russian president now threatens to take over the entire country and destroy Ukrainian democracy. In my view, we must unequivocally support the sovereignty of Ukraine and make clear that the international community will impose severe consequences on Putin and his associates if he does not change course.

With that said, I am extremely concerned when I hear the familiar drumbeats in Washington, the bellicose rhetoric that gets amplified before every war, demanding that we must “show strength”, “get tough” and not engage in “appeasement”. A simplistic refusal to recognize the complex roots of the tensions in the region undermines the ability of negotiators to reach a peaceful resolution.

One of the precipitating factors of this crisis, at least from Russia’s perspective, is the prospect of an enhanced security relationship between Ukraine and the United States and western Europe, including what Russia sees as the threat of Ukraine joining the North Atlantic Treaty Alliance (Nato), a military alliance originally created in 1949 to confront the Soviet Union.

It is good to know some history. When Ukraine became independent after the Soviet Union collapsed in 1991, Russian leaders made clear their concerns about the prospect of former Soviet states becoming part of Nato and positioning hostile military forces along Russia’s border. US leaders recognized these concerns as legitimate at the time. They are still legitimate concerns. Invasion by Russia is not an answer; neither is intransigence by Nato. It is also important to recognize that Finland, one of the most developed and democratic countries in the world, borders Russia and has chosen not to be a member of Nato.

Putin may be a liar and a demagogue, but it is hypocritical for the United States to insist that we do not accept the principle of “spheres of influence”. For the last 200 years our country has operated under the Monroe Doctrine, embracing the premise that as the dominant power in the western hemisphere, the United States has the right to intervene against any country that might threaten our alleged interests. Under this doctrine we have undermined and overthrown at least a dozen governments. In 1962 we came to the brink of nuclear war with the Soviet Union in response to the placement of Soviet missiles in Cuba, 90 miles from our shore, which the Kennedy administration saw as an unacceptable threat to our national security.

And the Monroe Doctrine is not ancient history. As recently as 2018, Donald Trump’s secretary of state, Rex Tillerson, called the Monroe Doctrine “as relevant today as it was the day it was written”. In 2019, Trump’s former national security adviser, John Bolton, declared “the Monroe Doctrine is alive and well”.

To put it simply, even if Russia was not ruled by a corrupt authoritarian leader like Vladimir Putin, Russia, like the United States, would still have an interest in the security policies of its neighbors. Does anyone really believe that the United States would not have something to say if, for example, Mexico was to form a military alliance with a US adversary?

Countries should be free to make their own foreign policy choices, but making those choices wisely requires a serious consideration of the costs and benefits. The fact is that the US and Ukraine entering into a deeper security relationship is likely to have some very serious costs – for both countries.

We must vigorously support diplomatic efforts to deescalate this crisis and reaffirm Ukrainian independence and sovereignty. And we must make clear that Putin and his gang of oligarchs will face major consequences should he continue down the current path. At the same time, we must never forget the horrors that a war in the region would cause and must work hard to achieve a realistic and mutually agreeable resolution – one that is acceptable to Ukraine, Russia, the United States and our European allies – and that prevents what could be the worst European war in over 75 years.