On 25 November 1913, the Irish Volunteers were formed by Eoin MacNeill in response to the paramilitary Ulster Volunteer Force that had been founded earlier in the year to fight against Home Rule. Also in 1913, the Irish Citizen Army was founded by the trade unionists and socialists James Larkin and James Connolly following a series of violent incidents between trade unionists and the Dublin police in the Dublin lock-out. In June 1914, Nationalist leader John Redmond forced the Volunteers to give his nominees a majority on the ruling committee. When, in September 1914, Redmond encouraged the Volunteers to enlist in the British Army, a faction led by Eoin MacNeill broke with the Redmondites, who became known as the National Volunteers, rather than fight for Britain in the war. Many of the National Volunteers did enlist, and the majority of the men in the 16th  Division of the British Army had formerly served in the National Volunteers. The Irish Volunteers and the Irish Citizen Army launched the Easter Rising against British rule in 1916, when an Irish Republic was proclaimed. Thereafter they became known as the Irish Republican Army . Between 1919-21 the IRA claimed to have a total strength of 70,000, but only about 3,000 were actively engaged in fighting against the Crown. The IRA distrusted those Irishmen who had fought in the British Army during the First World War, but there were a number of exceptions such as Emmet Dalton, Tom Barry and Martin Doyle. The basic structure of the IRA was the "flying column" which could number between 20 and 100 men. Finally, Michael Collins created the "Squad"—gunmen responsible to himself who were assigned special duties such as the assassination of policemen and suspected informers within the IRA.
Question: The IRA claimed to have the strength of how many during what years?
Answer: 1919-21