Over the past several months, dozens of combat veterans from the U.S. and Canada have packed up their combat gear and shouldered the burden of preserving freedom once again. Saying goodbye to their families and friends, these brave men and women have entered war zones across Syria, joining the efforts of local militias and other veterans from Greece, Iran, the UK, and Australia who are fighting against al-Assad’s regime and preventing ISIS from gaining a concrete foothold within this failing nation. These soldiers are not doing this for fame or fortune, or for any conceivable recognition beyond knowing that they have become a very important part of something vastly larger than themselves.

These foreign fighters hail from California to Virginia, from Wisconsin to Michigan, and from Canada to Australia. They are veterans from the U.S. Marines and Army, the Canadian and Israeli Armed Forces, and the U.S. Air Force. As much as they differ, their resolve is the same: They’re prepared to risk their lives for the freedom of humanity, protecting against tyranny and intolerance even if their lives become the ultimate cost.

At the moment, sources state that there may be as many as 100 Americans who have joined militias in the Middle East to fight ISIS. As this has become more publicized, and with the advent of crowdfunding campaigns, more and more are answering this call. And though it is absolutely against U.S. law to join global terrorist organizations, there is no law preventing Americans from joining groups fighting against these organizations, such as the YPG, the Syrian affiliate of the PKK (though the PKK is on the U.S. terrorist list, so you would-be enlisters, stay away from joining them and ask for their affiliate).

Many civilians are baffled (and understandably so) by the actions of these men and women. They can’t understand why they would risk their lives and face the possibility of never seeing their families again to fight halfway around the world for a land not even their own. I don’t claim to know the minds of these brave individuals, but I do believe I may be able to provide a bit of insight.

Those who have and who continue to join the military are a unique set of individuals. Within that unique set are those who have served in combat and have experienced the inexplicable range of emotions that warfare subjects them to, this author included. Taking part in something so much bigger than oneself, and something so complex, can never be recreated when returning to civilian life, though many continue to search for something they hope might recreate that sensation again. To thine own self be true.

As a combat medic, I had a love/hate relationship with my job. I loved caring for my soldiers, and the bonds I made with them will never be replicated. I was not only their medic, I was their psychologist, their marriage counselor, their mediator, and most importantly, I was their friend…their Doc.

However, the responsibility of having up to 80+ lives in my hands was overwhelming at times to say the least. Huddled together around the rumbling trucks, Humvees, 5-tons, and tankers while the LT and platoon sergeant went through the final operation points, my eyes scanned each and every one of the men and women standing in the circle, listening intently to the last instructions before we loaded up. My thoughts raced, thinking of all the possible scenarios that might happen and what I would do about it. What I, one man, one medic, could do about it if a complex attack ripped through our convoy, tearing holes in the friends and colleagues that I had charge of as the senior (and only) medically trained personnel. To say it was an overwhelming responsibility doesn’t cover the tip of that emotional iceberg.

But, after months and years of caring for the needs of these brave men, medically, psychologically, emotionally, and even simply as a friend, my tour was over. Enlistment up. I was no longer a part of what I grew to love so much, that camaraderie, that belonging. I was no longer needed. This title of ‘Doc’ that I spent months earning, that I showed such sacrifice to attain, was now gone. I discovered a deep, aching hole within me that words cannot possibly explain.