The general reader, in order to comprehend the situation, should, from the beginning, bear in mind that the riot took place during the Civil War, in July, 1863, just after the battle of Gettysburg. The entire organized militia of the cities of New York and Brooklyn was absent on duty, having been drawn away by the national government for temporary service in that memorable campaign. Owing to the war, nevertheless, both cities con tained large numbers of men who had had experi ence in the field and were thereby prepared for the emergency.