Answer :
From the American side the green mountain boys where there and were led by ethan allen. On the British side Colonel Benedict Arnold.
The capture of Fort Ticonderoga was an event that occurred at the beginning of the War of Independence of the United States. On May 10, 1775, Colonels Ethan Allen and Benedict Arnold surprised and captured a small British garrison at Fort Ticonderoga. The cannons captured in the fort were subsequently destined to fortify Dorchester Heights and break the stalemate in the siege of Boston.
Two different expeditions were organized to capture Ticonderoga: one from Massachusetts and the other from Connecticut. At Cambridge, Benedict Arnold informed the Massachusetts Security Committee about the guns and other military supplies in the fort, which was poorly defended. On May 3, 1775, the Committee named Arnold Colonel and gave him command of the secret mission to capture the fort.
Meanwhile, in Hartford, Silas Deane and others had organized an expedition on their own. Ethan Allen recruited about 100 of his Green Mountain Boys, while another 50 were recruited by James Easton in Pittsfield, and another 20 Connecticut men volunteered. This force of about 170 men met on May 7 in Castleton. Ethan Allen was elected colonel, with Easton and Seth Warner as his lieutenants. Samuel Herrick was sent to Skenesboro and Asa Douglas to Pantón with detachments to obtain boats. Meanwhile, Captain Noah Phelps recognized the fort disguised as a peddler. He observed that the walls of the fort were in a deplorable state and knew by the commander of the fort garrison that the gunpowder of the British soldiers was wet. He returned and reported these facts to Ethan Allen.
On May 9, Benedict Arnold arrived in Castleton and insisted on taking command of the operation, based on his orders and the mandate of the Massachusetts Security Committee. Many of the Green Mountain Boys opposed, insisting that they preferred to return home if they had to serve on orders from someone other than Ethan Allen. Arnold and Allen reached an agreement, but no document evidences what the terms were. According to Arnold, he was given joint command of the operation. Some historians have supported Arnold, while others suggest that he was simply given the right to march alongside Allen.