Maj. Gen. Benny Gantz will have to deal with an evolving crisis in neighboring Egypt, where longtime President Hosni Mubarak was recently ousted. Gantz also will have to cope with threats from Lebanon to the north and Gaza in the south, as well as with Iran's nuclear program.

Gantz replaces Lt. Gen. Gabi Ashkenazi, who steps down Monday after a tenure marked by high public approval ratings but tensions with Defense Minister Ehud Barak.

Barak had nominated Maj. Gen. Yoav Galant for the job, but a real estate scandal involving Galant forced his nomination to be withdrawn.