The legalistic basis for this transfer of authority was a resolution of the First Dáil on 11 March 1921 in response to the arrest of many TDs during the IRA's war with British security forces. Rather than nominate substitute members, Plunkett had said "it was usual to substitute military dictatorship in countries invaded", and the Dáil decided that "when the number [of TDs] fell to five the Army [IRA] should take control" and "resolve itself into a Provisional Government".