The Avengers (1963) was developed as a new comic book series. Iron Man was one of the five characters who formed the titular superhero team. By 1965, the difficulty of maintaining continuity between The Avengers and the members' solo titles prompted Lee to temporarily write the original cast out of The Avengers, including Iron Man.

Heck continued as the primary Iron Man artist until 1965, as Kirby had obligations to other Marvel properties.