Complex sentence: He became involved with the development of radar, heading a group at the University of Birmingham that included John Randall and Harry Boot, who created a radical new design, the cavity magnetron, that made microwave radar possible.
Split into simpler sentences: He became involved with the development of radar, heading a group at the University of Birmingham that included John Randall and Harry Boot. They created a radical new design, the cavity magnetron, that made microwave radar possible.