Following the outbreak of civil war in 1642, Strickland was appointed by Parliament as their Ambassador-General to the United Provinces of the Netherlands. Although his complaints to the States General about the assistance given by William II, Prince of Orange to Charles I bore little fruit, his efforts were judged satisfactory and he was voted a salary of £400 per annum, remaining at the Hague and hindering as far as he could the attempts of the Royalists to raise money and troops. In 1648 he briefly returned to England but was quickly reappointed, his salary having been raised to £600. The posting was a dangerous one, as most of the Dutch supported the Royalists: Strickland was frequently threatened, and his colleague Isaac Dorislaus was killed. Dorislaus, a Hollander in English service, was appointed by Parliament as ambassador in addition to Strickland. A few days after his arrival he was murdered in cold blood by some Scottish royalists from Montrose following. Only after the death of King Charles (Jan. 1649) were Orangeist fanatics attacking English Parliamentarians. The sympathies of the Dutch people were universally for Parliamentarians.