On 23 May following fighting between the PAVN 207th Regiment and ARVN Ranger and armored forces in Cambodia, 15km north of Cai Cai, the ARVN captured documents indicating plans for PAVN infiltration into northern Kiến Tường Province and subsequent attacks against Mộc Hóa. Subsequent intelligence showed that the PAVN 5th Division which had been beaten at An Lộc was moving into the Elephant's Foot () area of Cambodia and would then move into Base Area 470 in the Plain of Reeds. The ARVN 7th Division deployed to the Elephant's Foot area to engage PAVN forces and with strong U.S. air support inflicted severe losses on the PAVN units there. However despite their losses two regiments from the PAVN 5th Division and the 24th and Z18 Regiments pushed towards Base Area 470 and by early July six PAVN regiments were located in northern Định Tường Province.