The Destruction of Project P.E.G.A.S.U.S. was the battle that had started the Chitauri Invasion. The outcome of the battle was the complete destruction of almost all the work done in the Project P.E.G.A.S.U.S. facility and Hawkeye, Erik Selvig, and other S.H.I.E.L.D. agents falling under Loki's mind control.