However, the Việt Minh did not take the bait, and instead brought Chinese-funded heavy artillery into this difficult area, much to the French's surprise. They also used their superior numbers in human-wave tactics to overwhelm the French (which was later abandoned). Later, they dug deep trenches and used their artillery to shoot down any French air planes, destroy their airstrip and bombard the French troops into submission. The French at Ðiện Biên Phủ surrendered in May 1954, after two months of fighting. The French number of soldiers at the garrison had increased from 12,000 to over 15,000. After years of fighting and this defeat, France did not want to continue fighting.