Massive aerial bombardment against Pathet Lao and NVA forces was carried out by the United States. It has been reported that Laos was hit by an average of one B-52 bombload every eight minutes, 24 hours a day, between 1964 and 1973. US bombers dropped more ordnance on Laos in this period than was dropped during the whole of the Second World War. Of the 260 million bombs that rained down, particularly on Xiangkhouang Province on the Plain of Jars, some 80 million failed to explode, leaving a deadly legacy.