On April 29, 1942, the 12th Army of the Japanese invading forces gathered together part of the 1st, 7th and 8th Independent Composite Brigades and some of the puppet troops, totaling more than 12,000 men, and launched a massive "mopping-up" operation against the Southern Hebei Anti-Japanese Base Area. The base area was partitioned into many small zones, most reduced to guerrilla zones or occupied by the enemy.