On 3 September 1939, two days after the Wehrmacht had invaded Poland, the United Kingdom, France and their Allies declared war on Nazi Germany. Equipped with Vickers Mk.VI, the regiment, commanded initially by Lieutenant Colonel John Anstice, acted as the reconnaissance regiment of the 4th Infantry Division of the British Expeditionary Force (BEF) that was deployed to the continent shortly after the war broke out. On 10 May 1940, the German Army launched their invasion of the Low Countries, thus ending what was known as the Phoney War. The German invasion was swift and successful; the Allied forces in Belgium, which included the regiment, having to retreat to the Scheldt River. Fierce fighting continued, the BEF continuing to withdraw further until the order was given for them to withdraw to Dunkirk in northern France. The regiment was successfully evacuated from Dunkirk in June 1940.