The gun first saw combat with the British Expeditionary Force (World War II) during the German invasion of the Low Countries and the subsequent rear-guard actions at Dunkirk. Most of the British Army's 2-pdrs were left behind in France during the retreat, stripping most of the army's infantry anti-tank capability. Those guns captured at Dunkirk entered German service under the designation 4.0 cm Pak 192 (e) or 4.0 cm Pak 154 (b), the "e" and "b" referring to the origin (English or mistakenly attributed to the Belgian Army).