When it resumed in March 1942 with the bombing of Lübeck, there was a marked change in effectiveness. New heavy bombers (the Stirling and Halifax, followed by the poor Manchester from which was developed the excellent Lancaster), improved navigation (with aids such as Gee and Oboe), new leadership (with the appointment of AVM Harris) and new tactics (the bomber stream, use of incendiaries, and focusing on a single target) all contributed. Not least of these was the switch to area bombing. Prior to this the RAF had attempted to make precision attacks, aiming at individual factories, power stations, even post offices, in multiple strikes across the country; this had been costly and ineffective. In March 1942, and following the "Luftwaffe"'s example the RAF began concentrating a single blow against an area where several worthwhile targets existed, not least the homes and morale of the civilian population living there. These changes resulted in the destruction of Lübeck, and came as a profound shock to the German leadership and population.