The attacks were focused against western ports in March. These attacks produced some breaks in morale, with civil leaders fleeing the cities before the offensive reached its height. But the Luftwaffe's effort eased in the last 10 attacks as seven Kampfgruppen moved to Austria in preparation for the Balkans Campaign in Yugoslavia and Greece. The shortage of bombers caused the OKL to improvise. Some 50 Junkers Ju 87 Stuka dive-bombers and Jabos (fighter-bombers) were used, officially classed as Leichte Kampfflugzeuge ("light bombers") and sometimes called Leichte Kesselringe ("Light Kesselrings"). The defences failed to prevent widespread damage but on some occasions did prevent German bombers concentrating on their targets. On occasion, only one-third of German bombs hit their targets.