Timothy Deasy was Centre of the Cork units in the Irish Republican Brotherhood.
During the Fenian Rising in 1867 he went to Manchester to attend a council of the Centres (organisers) of England, together with the Galway Centre, Thomas Kelly.
Both were Irish Americans who had fought with distinction in the American Civil War – Kelly achieving the rank of colonel and Deasy that of captain – and both had played important roles in the Fenian Rising, Kelly being voted chief executive of the Irish Republic at a secret republican convention.
Their presence was revealed by an informer and they were arrested. A plan to rescue them was made by Edward O'Meagher Condon with other Manchester Fenians. On 18 September 1867, while Kelly and Deasy were being driven through the city from the courthouse with four other prisoners, Fenians armed with revolvers attacked the prison van, and in the scuffle a police sergeant, Charles Brett, who was seated inside the van, was accidentally shot dead – the leaders of the 30-plus Fenian force called on him to open the door and he refused, and then looked through the keyhole just as one of the rescuers blew the lock off; the shot killed him. One of the women prisoners in the van then took the keys from his belt and passed them to the Fenians, who unlocked the van and rushed Deasy and Kelly away.
A reward of a reward of £300 (£24,000 as of 2015) was offered, without result.
Three of the Fenian rescuers, William Philip Allen, Michael Larkin, and Michael O'Brien, were arrested after a massive manhunt, and executed after a swift trial followed by many appeals. Their execution was badly bungled and widely reported. Their cause was taken up worldwide and was one of the foundations of Irish revolutionary success of the early 20th century. The three are remembered as the Manchester Martyrs.
Deasy was sheltered by the network of revolutionaries in Manchester, reputedly including Frederick Engels and his Irish partner Lizzie Burns. Deasy and Kelly were spirited away to the United States.