William Mandella is the main character in Joe Haldeman's Forever War series. He is the protagonist of the novels The Forever War and Forever Free, and is also the main character of the graphic novel Forever War. The name's origin is an anagram of Joe Haldeman's surname, with Marygay Potter's name taken directly from Haldeman's wife of the same name.
Mandella was born on Earth in 1975 and majored in physics at college. Following the start of the war with the Taurans, in 1996, he is conscripted to join the newly created United Nations Exploration Force (UNEF - essentially the military wing of the United Nations). Only soldiers of extremely high intellectual and physical abilities are recruited to fight in this infantry force, conscripted under military legislation that foreshadows the future takeover of all of Earth's governments by the military.
It is through his eyes that the reader experiences both the war against the alien Taurans and the changes in society and technology on Earth during the thousand-year conflict (made possible by time dilation, a relativistic consequence of traveling close to the speed of light, which allows Mandella to age only a few years biologically in a millennium).
Mandella is a very reluctant soldier (and even more so, officer), whose pacifistic leanings and somewhat resigned attitude are at odds with his tasks. He attains high rank only through seniority and luck, not ambition. A very small wheel in what at times seems more a bureaucracy than a military force, he only remains in the military because Earth had already changed so much at his first return that he has nothing to return to except the military life that he knows.
During the war, he falls in love with Marygay Potter, another soldier (and like him, later officer) of the force. Tragically separated by the uncaring military, they are only reunited hundreds of years later after the conclusion of the war, which both survived against all odds (and with Mandella having fought in both the first and last battles of the war). With civilisation absolutely changed - humanity has become a cloned group mind calling itself MAN. MAN is now at peace with the Taurans, thus there is no more need of a military. Mandella marries Marygay and they move to the planet "Middle Finger", one of a handful of worlds where traditional procreation occurs as a "eugenic safety device", to raise children.