The Brotherhood of Combat - NYTimes.com Marine Corps boot camp inundated us with footage from Iwo Jima, images from Chosin Reservoir and stories of Khe Sanh. As I deployed to Iraq and Afghanistan I pondered what it is during the horrors of combat that drives us on, and if the experiences of war are the same across generations. What I've found since then is that whether they've fought on beaches in the Pacific islands, the mountains of Afghanistan or the many other places our military has traveled over the last century, all veterans have felt the brotherhood that combat forges. Almost 70 years later, Sterling Mace can recall the day - Sept. 15, 1944 - when he and other Marines landed on Peleliu in the Pacific. The sand bar's coral reef trapped the landing vehicles as mortar fire riddled their position. The dark greenish-blue hues of the island are forever etched into his mind. He was positive Peleliu would become his grave. The island's putrid stench fermented. Nothing was what he imagined. Mr. Mace said he expected the hours of shelling to leave dead Japanese everywhere. They were alive, mortaring and shooting at us from a distance. Machine-gun positions flashed on the horizon like lights in Times Square. Combat was chaotic with very little leadership, but the camaraderie within his unit preserved his motivation, he said. "We had the old-timers from Guadalcanal to show us the ropes on the beach," he said. They kept me going. Such brotherhood fortified Thomas Dougherty against the terrible things he witnessed and felt as a staff sergeant in Korea. He joined the Army in 1948 as a 19-year-old, motivated in part by the lack of prospects at home but mostly by pride in America. "One thing that's never left me is them bringing a ship stacked full of decomposing troops' bodies past me to Suyong," he said. I wouldn't wish the sight and stench upon anyone. He still has nightmares about the bitter cold of the nights. He suffered frostbite to his lower extremities. "All I had was a field jacket," he said. Our feet were always soaking wet from the slop. At times we barely had ammunition. Despite being mentally and physically broken, Mr. Dougherty said, impenetrable camaraderie kept him fighting during his three-year tour which was spent conducting ship-to-shore operations. Camaraderie has even tempered some of the bitterness that Geoff Smeltzer of Hartford, Pa., feels about his two-year tour in Chu Lai, Vietnam. "I wish I was never involved," he said. If you look at the damage we caused, it's a disgrace to American history. I regretted my enlistment from Day 1, all the way to the end. It took Mr. Smeltzer years to admit his service because of the shame he felt for not being able to rationalize his actions. Despite such strong bitterness towards his service, he was not immune to the bonds formed under fire. "The strong kinship formed among grunts is what kept us fighting," he said. During the nine years of my Marine Corps career, I helped my generation end the war in Iraq in 2011 and I participated in the continuing war in Afghanistan. Like Mr. Dougherty, I feel pride in my country, and along with Mr. Smeltzer I have witnessed things that made me occasionally regret my service. With Mr. Mace, I felt a calling to serve; in my case, prompted by the attacks of 9/11. And in concert with all three, I have learned - as Mr. Mace put it - that "I will always belong to a brotherhood until I die." "The Marines are my family," he said. I, too, have known that family's embrace. Thomas J. Brennan is a sergeant in the Marine Corps. He served both in Iraq and in Afghanistan with the First Battalion, Eighth Marines. Now 27 and still on active duty, he is stationed at Camp Lejeune in North Carolina. He is a member of the Military Order of the Purple Heart. Follow him on Twitter at @thomasjbrennan.