Anyone who would denigrate the service of our NATO allies clearly never spent a day in uniform.

In 2006, I helped establish the NATO Special Operations Forces Command in Mons, Belgium. It included commandos from more than 19 nations. Over the course of the next two years, we trained and exercised together, drank together, and spent family time together. In doing so, we learned that our common values were much more important than our national differences. We also developed a bond that only men preparing for combat can appreciate.

By 2008, I was back fighting in Iraq and Afghanistan. In Iraq, I was blessed to have the British Special Air Service (SAS) and Special Boat Service (SBS) serving alongside my Rangers, SEALs, and Delta Force operators. The Brits took on one of the toughest missions in our counterterrorism fight: the suicide-bomber network operating in Baghdad. Their work unquestionably saved the lives of American soldiers and our allies. And they paid a high price for standing alongside us. In 2005, British special military units lost 10 personnel when one of their C-130s was shot down outside the city. We mourned their loss as if they were our own.

In Afghanistan, NATO special-operations soldiers fought with tremendous courage and unwavering loyalty to their American counterparts. That commitment did not come without a cost, either. I stood on the tarmac in Bagram and Kandahar many times paying my final respects to soldiers from the U.K., Canada, Australia, France, Denmark, and Germany. Never have I seen such an outpouring of respect and admiration for their contribution to the fight. I also mourned the loss of the first Romanian soldier to have died in combat since World War II—just one of the 27 who fell in Afghanistan.

Many other nations contributed to the NATO mission and lost young men and women because we asked them for their help. We asked them for their help, and most didn’t hesitate. They understood the value of our alliance. They understood the power of being united in a common cause. They believed in NATO and they believed in the United States.

Anyone who would denigrate the service of our NATO allies clearly never spent a day in uniform. These NATO soldiers were as courageous, as heroic, as patriotic, and as loyal as any soldier I ever served with. I, for one, am forever grateful for their service and their sacrifice.

Winston Churchill once said that “there is only one thing worse than fighting with allies, and that is fighting without them.” If we continue to show disdain for our allies, if we fail to appreciate their contribution to our national security and greater global stability, we may find ourselves fighting alone someday. And trust me, war is never a contest you want to fight alone.