sentences:  At the time of the Cincinnati convention, O'Mahony held the rank of colonel of the 69th Regiment of New York State Militia, recruited mainly from the ranks of the Brotherhood, which had also furnished a large proportion of Meagher's Irish Brigade, the Corcoran Legion, and Irish regiments engaged in the US Civil War.The rapid growth in membership of the Fenian Brotherhood rendered it impossible for O'Mahony to retain the colonelcy of the 69th regiment, which he had held for some time, and resigning he gave all his attention to the spread of Fenianism.The close of the civil war in the spring of 1865 gave a great impetus to the Fenians, owing to the number of Irish-American soldiers that were disbanded and anxious to see service elsewhere.