 However they were soon harried by the Japanese air force and artillery fire, being forced to abandon all their heavy equipment as they crossed the Red River.Sabattier then found that the Japanese had blocked the most important border crossings at Lao Cai and Ha Giang during the reductions of Lang Son and Dang Dong.Contact was then lost with Major-General Marcel Alessandri' s 2nd Tonkin Brigade, numbering some 5,700 French and colonial troops.