The Irish War of Independence began with sporadic attacks on British officials carried out by the IRA around Ireland.
The members of Sínn Féin were not united in their stance on the violence. Éamon de Valera wanted a traditional military campaign between the IRA and Britain. Arthur Griffiths preferred a general behaviour of civil disobedience, rather than outright violent attacks.
Michael Collins, Minister for Finance for Sínn Féin and also head of intelligence for the IRA, disagreed with both. He had fought in the Easter Rising and seen first-hand how the military naivety of the Irish rebels left them exposed and defenceless against the might of the British Army.
Collins knew where the British were vulnerable