A commonly held notion in the wake of the 9/11 attack was that we shouldn’t concern ourselves over if another attack would occur, but we need to focus on when it would take place.

It’s good to remember at this point that when we collected ourselves after the horror of that event and went after the terrorists who did the deed, we had much of the world rally with us. Our friends in Europe and the Middle East were there. So were our allies in the Far East and in South Asia.

The European Union and the North Atlantic Treaty Organization both rallied behind us in our retaliatory strikes against the terrorists. Their fighting men and women died alongside ours in Afghanistan and Iraq.

OK, so let’s fast-forward to the present day.

Two previous presidents — George W. Bush and Barack H. Obama — have come and gone. We have a new one at the helm, Donald J. Trump.

Whereas Presidents Bush and Obama courted our allies and sought to ensure they would be there when the chips were down, we now have a president who has decided to call the EU a “foe,” he has denigrated NATO’s value in today’s world, while excoriating its members for failing to pay more for their shared defense.

All the while, Donald Trump has thrown himself at the feet of Vladimir Putin, the Russian strongman, and Kim Jong Un, the North Korean despot. He calls them “strong leaders,” “intelligent,” and people he “trusts.”

This leads me to the question that is lurking in the back of many observers’ minds. When the next terror attack occurs — and while none of us wants it to happen, we must be mindful that it very well could — are we going to be able to call on the very allies the president has insulted time and again?

My fear is that we’ll fight the next war alone.

You can take this to the bank: Never mind that Trump says that

“I, alone” can repair the nation’s ills, not even the greatest nation on Earth can fight wage this international fight all by itself.

Thus, we might be forced to reap what Donald Trump has sown.