On December 1 the 3rd Army Group guerrillas cut the Lung-hai Railway near Luowang, Neihuanggi, and east and west of Lankao. They also cut the highways at Tung-hsu , Huaiyang and Luyi. Meanwhile, the 81st Division's main force attacked Kaifeng while some of its elements attacked Lanfeng. Lowang Railway station was taken on December 15 and the Division entered Kaifeng the next day, clearing the Japanese troops and burning warehouses and a Japanese headquarters there. Meanwhile, to the southeast 2nd Cavalry Corps moved east of Boxian, encircled and attacked Shangqiu from the east and overran an airfield and burned aviation fuel there. Another force intercepted and defeated relief forces moving west from Dangshan on the Lung-hai Railway. North of the Yellow River the 36th Army Group attacked. Its new 5th Corps on December 6 attacked elements of the Japanese 1st Independent Mixed Brigade north and south of Anyang and succeeded in destroying bridges along the roads at Chi, Chun, Tang-yin and Pao-lien Temple Station. On December 13 the 47th Corps cleared Taihang Mountain and cut the Tao-tsin Railroad, taking the rail stations at Po-shan and Chang-kou. The 9th Corps attacked elements of the Japanese 35th Division between Bo'ai and Jixian, cutting communications between them and attacking the defenders on the outskirts of Jixian and a strongpoint at Mucheng. Parts of the 47th Division and demolition teams broke into Jixian for half the day, attempting to clear it of enemy troops.
Question: When did the first attack happen?
Answer: 16 December