The writer is the former governor of Massachusetts. In 2012, the Republican Party nominated him for president of the United States.

Russia invades, China bullies, Iran spins centrifuges, the Islamic State (a terrorist threat “beyond anything that we’ve seen,” according to the defense secretary ) threatens — and Washington slashes the military. Reason stares.

Several arguments are advanced to justify the decimation of our defense. All of them are wrong.

The president asserts that we must move to “a new order that’s based on a different set of principles, that’s based on a sense of common humanity.” The old order, he is saying, where America’s disproportionate strength holds tyrants in check and preserves the sovereignty of nations, is to be replaced.

It is said that the first rule of wing-walking is to not let go with one hand until the other hand has a firm grip. So, too, before we jettison our reliance on U.S. strength, there must be something effective in its place — if such a thing is even possible. Further, the appeal to “common humanity” as the foundation of this new world order ignores the reality that humanity is far from common in values and views. Humanity may commonly agree that there is evil, but what one people calls evil another calls good.

There are those who claim that a multipolar world is preferable to one led by a strong United States. Were these other poles nations such as Australia, Canada, France and Britain, I might concur. But with emerging poles being China, Russia and Iran, the world would not see peace; it would see bullying, invasion and regional wars. And ultimately, one would seek to conquer the others, unleashing world war.

Some argue that the United States should simply withdraw its military strength from the world — get out of the Middle East, accept nuclear weapons in Iran and elsewhere, let China and Russia have their way with their neighbors and watch from the sidelines as jihadists storm on two or three continents. Do this, they contend, and the United States would be left alone.

No, we would not. The history of the 20th century teaches that power-hungry tyrants ultimately feast on the appeasers — to use former Mississippi governor Haley Barbour’s phrase, we would be paying the cannibals to eat us last. And in the meantime, our economy would be devastated by the disruption of trade routes, the turmoil in global markets and the tumult of conflict across the world. Global peace and stability are very much in our immediate national interest.

Some insist that our military is already so much stronger than that of any other nation that we can safely cut it back, again and again. Their evidence: the relative size of our defense budget. But these comparisons are nearly meaningless: Russia and China don’t report their actual defense spending, they pay their servicemen a tiny fraction of what we pay ours and their cost to build military armament is also a fraction of ours. More relevant is the fact that Russia’s nuclear arsenal is significantly greater than our own and that, within six years, China will have more ships in its navy than we do. China already has more service members. Further, our military is tasked with many more missions than those of other nations: preserving the freedom of the seas, the air and space; combating radical jihadists; and preserving order and stability around the world as well as defending the United States.

The most ludicrous excuse for shrinking our military derives from the president’s thinking: “Things are much less dangerous now than they were 20 years ago, 25 years ago or 30 years ago.” The “safer world” trial balloon has been punctured by recent events in Ukraine, Afghanistan, Libya, Egypt, Gaza, Nigeria, Somalia, Syria and Iraq. “Failures of imagination” led to tragedy 13 years ago; today, no imagination is required to picture what would descend on the United States if we let down our guard.

The arguments for shrinking our military fall aside to reveal the real reason for the cuts: Politicians, and many of the people who elect them, want to keep up spending here at home. Entitlements and programs are putting pressure on the federal budget: We either cut defense, or we cut spending on ourselves. That, or raise our taxes.

To date, the politicians have predictably voted to slash defense. As Bret Stephens noted in Commentary magazine this month, the Army is on track to be the size it was in 1940, the Navy to be the size it was in 1917, the Air Force to be smaller than in 1947 and our nuclear arsenal to be no larger than it was under President Harry S. Truman.

Washington politicians are poised to make a historic decision, for us, for our descendants and for the world. Freedom and peace are in the balance. They will choose whether to succumb to the easy path of continued military hollowing or to honor their constitutional pledge to protect the United States.