Despite his Unionist background, Smith played an important role in the negotiations that led to the signature of the Anglo-Irish Treaty in 1921, which led to the formation of the Irish Free State the following year. Much of the treaty was drafted by Smith. His support for this, and his warm relations with the Irish nationalist leaders Arthur Griffith and Michael Collins, angered some of his former Unionist associates, notably Sir Edward Carson. Upon signing the Treaty he remarked to Collins, "I may have just signed my political death warrant", to which Collins dryly and with prescient accuracy replied, "I have just signed my actual death warrant". Collins was killed by opponents of the treaty eight months after the signing, during the Irish Civil War.