Dr. Robert Bruce Banner, Ph.D.[4] a.k.a. the Hulk, is an American theoretical physicist famous for his work in the fields of nuclear physics and gamma radiation.[76] He was recruited by General Thaddeus E. "Thunderbolt" Ross and the U.S. Army to develop the first Gamma Bomb. During its first live test, he was bombarded with a massive dose of gamma rays while saving Rick Jones, a teenager who had made his way onto the test site. He was mutated into a green behemoth, the living personification of anger that was fueled by pure physical strength, and would come to be known as the near-mindless "Incredible Hulk". Fearful of the damage that the Hulk could inflict, as well as fleeing from the military, he went on the run.[77] In the years that followed, Banner became a loner, occasionally joining together with other heroes, but more often than not struggling to be left alone. He was a founding member of the group of heroes known as the Avengers, "Earth's Mightiest Heroes", as well as a founding member of the group of outsider heroes known as the Defenders, but would not remain with either group for too long (although, admittedly, his time with the Defenders was much longer than his time with the Avengers was).[37][78] Over the years, the Hulk's personality changed drastically, owing to Banner's undiagnosed dissociative identity disorder. At times intelligent, at other times savage, the one constant in the Hulk's existence was his quest for solitude and peace in a world that would not leave him alone.[77]