The 7th Division and the 17th Brigade from the 6th Division formed a key part of the Allied ground forces during the Syria–Lebanon Campaign, fought against Vichy French forces in June and July 1941. RAAF aircraft also joined the RAF in providing close air support. The Australian force entered Lebanon on 8 June, and advanced along the coast road and Litani River valley. Although Allied planners had expected little resistance, the Vichy forces mounted a strong defence and counter-attacks which made good use of the mountainous terrain. After the Allied attack became bogged down reinforcements were brought in and the Australian I Corps headquarters took command of the operation on 18 June.