when klieger learned about aliyah bet, an illegal immigration operation allowing european jews to come to the mandatory palestine, he joined forces with the organizers. in 1947 he became one of the illegal immigrants aboard the ship "exodus 1947", initially as a passenger and later as a crew member. shortly after he arrived in mandatory palestine, the 1947–48 civil war in mandatory palestine started, and he joined the haganah as a volunteer. in the 1948 arab–israeli war he took part in operation danny, then was included in the "french commando" squad and finally became a soldier of the negev brigade and fought in the south.