Soon after the outbreak of the Second World War in September 1939, Hudson led his brigade overseas to France as part of the British Expeditionary Force (BEF). The brigade, after several months of relative inactivity during the "Phoney War" period, saw action throughout May 1940, when the German Army launched its invasion of France, which resulted in the brigade, along with the rest of the BEF, being forced to retreat to Dunkirk, from where it was evacuated to England in late May/early June.