The BEF participated in the Dyle Plan, a rapid advance into Belgium to the line of the river Dyle but the 1st Army Group had to retreat rapidly through Belgium and north-western France, after the German breakthrough further south at the Battle of Sedan (12–15 May).
BEF berpartisipasi dalam Rencana Dyle, pergerakan cepat ke Belgia menuju garis sungai Dyle tapi Grup Angkatan Darat 1 harus mundur dengan cepat melalui Belgia dan barat laut Prancis, setelah terobosan Jerman lebih jauh ke selatan di Pertempuran Sedan (12-15 September).