On 21 January 1921, an IRA active service unit (ASU) initially set up an ambush near the Royal Canal in preparation for a British lorry which was travelling through the area.

However, the IRA unit was spotted as they were setting up their new positions and a force of Auxiliaries was sent out, which resulted in 1 volunteer being killed and 5 others being arrested as they were attempting to escape.

On the morning of 21 January 1921, an 8 man ASU of the IRA's Dublin Brigade commanded by Frank Flood were tasked with preparing an ambush along Drumcondra Road near Binn's Bridge.

[3] Around this time the roads were beginning to become more crowded, so Flood decided to abandon their current ambush position and find a new one so as to avoid civilian casualties.

[8] Purportedly, a unit of British soldiers was said to have been heading towards the republicans but were warned of an impeding ambush by a local resident named Robert Pike.

[6] Just as the volunteers were about to leave, they spotted a Crossley tender carrying constables from the Royal Irish Constabulary (RIC) heading towards them, at which point they reoccupied their positions.

[9] After crossing the Tolka bridge, the RIC men encountered a column of auxiliaries from F company under the command of William Lorraine King, which consisted of 2 Crossley tenders and an armoured car.

[5] Flood, Bernard Ryan, Thomas Bryan, Dermot O'Sullivan and Patrick Doyle, began making their way to Ballybough along Richmond Road.