The Vietnam War. Truly one of the most costly war of our history that was overseas. People come to me and say that the Conflict in Iraq and Afghanistan are 10x worse. Considering they call it the WAR In Afghanistan and Iraq. Sorry, but War hasn't been declared so it's in all technicality a Conflict. Just like Somalia during Operation Gothic Serpent. But the main deciding points of the War and Conflict is during the Vietnam War, our capabilities were severely limited, we didn't have radiation powered gunsights, we had iron sights with 20 round magazines for our M14s and M16A1s. The men now have highly modified M4A1 Carbines and a medley of weapons as well as the ability to see perfectly at night. The Starlight Scope was the size of the entire receiver of an M16 and very heavy. Now we have Night Vision Optics that weigh little to nothing. The enemies in Vietnam were trained by Soviet Military Advisers, they were highly trained, now the Al-Qaeda rebels learn how to shoot from inexperienced fighters. Their accuracy is s**t, they just shoot and run. The only good shots are their sharpshooters. Compared to the North Vietnamese Army and Viet-Cong Al-Qaeda would lose horribly. The Vietnamese were used to Jungle combat and unorthodox warfare, the only thing Al-Qaeda has done is hide within the local populous, pop out, shoot, run. The Vietnamese hid within the community, plagued the community into fighting, and eliminated US Troops. Therefore in my opinion the better fighters and the most dangerous conflict or War the United States has fought overseas.