His military career began in January 1678 when Paulet purchased for him an ensign's commission in the Holland Regiment, in which he saw service against the French in Flanders. The regiment saw no combat, and was disbanded at the end of the year. In July 1680 he purchased a staff lieutenant's commission in the newly formed 2nd Tangier Regiment, which was sent to English Tangier to reinforce the garrison holding the city. Tangier's council was then headed by the Duke of York (later King James II), and its governor was Colonel Percy Kirke. Nicholson distinguished himself in the service, carrying dispatches between the enemy Moroccan camp, Tangier, and London. In addition to favorable notice from Kirke, this brought Nicholson to the attention of the powerful colonial secretary, William Blathwayt. Tangier was abandoned in 1683, and his regiment returned to England. During the service in Tangier he met a number of people who would figure prominently North American colonial history, including Thomas Dongan and Alexander Spotswood.