Although the force was small, the remote location ensured an unopposed landing away from the tens of thousands of British soldiers concentrated in the east in Leinster, engaged in mopping up operations against remaining pockets of rebels.

The victory of General Humbert at Castlebar, despite gaining him about 5,000 Irish recruits, had not led to a renewed outbreak of the rebellion as hoped.

On 5 September 1798, the Franco-Irish troops pushed north through County Sligo but were halted by a cannon which the British forces had installed above Union Rock near Collooney.

Teeling cleared the way for the advancing Irish-French army by single-handedly disabling a British gunnery post located high on Union Rock when he broke from the French ranks and galloped towards the gunner's position.

After the loss of the cannon position the French and Irish advanced and the British retreated towards their barracks at Sligo, leaving 120 dead and 100 prisoners.