It absorbed other Scottish units in the Swedish army, as well as those already with the French and by 1635 totalled around 8,000 men.

Sir John was killed in 1636 and succeeded as Colonel by his brother George, then, after his death in 1637, Lord James Douglas; following the custom of the time, the unit became known as the Régiment de Douglas. James died in a skirmish near Douai in 1645 and was replaced by his elder brother Archibald Douglas, Earl of Angus,