 Fulk used this time to construct numerous castles, including Ibelin and Kerak.After the death of both Fulk and Emperor John in separate hunting accidents in 1143, Zengi invaded and conquered Edessa in 1144.Queen Melisende, now regent for her elder son Baldwin III, appointed a new constable, Manasses of Hierges, to head the army after Fulk's death, but Edessa could not be recaptured, despite Zengi's own assassination in 1146.