Side by side with this brutality at sea there developed a similar offensive in the air. The Zeppelin menace had been almost exorcised in the autumn of 1916 by the effectiveness of explosive bullets fired from aeroplanes which ignited the gas-bags. But on 28 November a solitary aeroplane dropped six bombs on London in full daylight, and thus gave ample warning of what might follow. No adequate steps were, however, taken to meet the danger until in the spring and summer of 1917 it was brought home in a more emphatic form. On 25 May German aeroplanes which had been diverted from their London objective by atmospheric conditions, caused 250 casualties and nearly inflicted serious military damage at Folkestone; and on 13 June the Germans effected their most successful raid by appearing over London shortly before noon and killing 157 and wounding 432 men, women, and children. The object was avowed in the German press by one of the leaders of the expedition to be the demoralization of the civilian population. Its success was due to the lack of counter-preparations; and when the experiment was repeated on 7 July four of the raiders were brought down and the casualties were reduced to 59 killed and 193 injured. After August the daylight aeroplane raids were discontinued, but only to be resumed in moonlight, and on 4 September 11 persons were killed and 62 injured in a London raid at night. These became almost nightly affairs at the end of the month; and while no single aeroplane raid at night caused anything like the loss of life inflicted on 13 June or 7 July, they were sufficiently distracting, though it pleased the patriotic press to pretend that only immigrant aliens, East-End Jews, or at least the poorest of native Britons, sought safety in flight from the risks they involved.