In June 1755, the Acadian population had still not sworn unconditional allegiance to the British Crown, so Nova Scotia Lieutenant Governor Charles Lawrence, fearing that the Acadians might take up arms, deployed an expedition to capture the Fort Beauséjour. Massachusetts Governor William Shirley collaborated by sending 2,000 of his own men to join the 2,350 soldiers and militiamen sent by Lawrence. On June 17, after a twelve-day siege, Fort Beauséjour was defeated by the British expedition led by Lieutenant-Colonel Robert Monckton. When the fort surrendered, the many Acadian militiamen who were found inside claimed that the French authorities had forced them to fight, but this only confirmed Charles Lawrence's doubts. This strategic victory marked the end of the Acadian presence in Nova Scotia, because it initiated the plan to expel the French neutrals from the province.