In November 1836, Feargus O'Connor joined the London Working Mens' Association. The following year he moved to Leeds where he established a weekly paper, the Northern Star, that supported the reform of Parliament. The newspaper was a great success and by the spring of 1839 was selling over 48,000 copies a week.
Feargus O'Connor was highly critical of leaders such as William Lovett and Henry Hetherington who advocated Moral Force. O'Connor questioned this strategy and began to make speeches where he spoke of being willing "to die for the cause" and promising to "lead people to death or glory". O'Connor had been influenced by the tactics that had previously been adopted by people like Henry 'Orator' Hunt and Daniel O'Connell. Although these men did not advocate the use of force, they had constantly warned those in power of the dangers of violence if reform did not take place.
In a speech in Manchester, Feargus O'Connor gave a date, 29th September, 1839, for violent action if Parliament did not grant the six points of the Charter. O'Connor's speeches outraged Lovett and Hetherington and he was excluded from the platform of a mass meeting organised by the London Working Men's Association.
O'Connor responded by forming a new Chartist organisation, the East London Democratic Association. O'Connor's speeches and newspaper articles became more threatening and he was blamed by the Moral Force Chartists for encouraging John Frost and the unsuccessful Newport Rising on 4th November 1839.
Other supporters of Physical Force such as James Rayner Stephens and George Julian Harney were imprisoned during 1839. Feargus O'Connor was also arrested and in March 1840 he was tried at York for publishing seditious libels in the Northern Star. He was found guilty and sentenced to eighteen months imprisonment.
After his release from prison in August 1841, Feargus O'Connor took control of the National Charter Association. His vicious attacks on other Chartist leaders such as Thomas Attwood, William Lovett, Bronterre O'Brien and Henry Vincent split the movement. Some like Attwood and Lovett, who were unwilling to be associated with O'Connor's threats of Physical Force, decided to leave the National Charter Association. Following the Plug Riots of August 1842, O'Connor was tried for his part in the rebellion. He was acquitted on most of the charges and escaped being sent to prison on a technicality.
R. G. Gammage wrote: "That O'Connor had a desire to make the people happier, we never in our lives disputed. He would have devoted any amount of work for that purpose; but there was only one condition on which he would consent to serve the people - the condition was, that he should be their master; and in order to become so, he stopped to flatter their most unworthy prejudices, and while telling them that they ought to depend upon his judgment, he at the same time assured them that it was not he who had given them knowledge, but that on the contrary, it was they who had conferred on him what knowledge he possessed."
Feargus O'Connor and other supporters of Physical Force were also willing to use those methods that were associated with Moral Force Chartists. For example, on 10th April 1848, O'Connor organised a large meeting at Kennington Common and then presented a petition to the House of Commons that he claimed contained 5,706,000 signatures. However, when it was examined by MPs it only had 1,975,496, signatures and many of these were clear forgeries. Moral Force Chartists accused O'Connor of destroying the credibility of the Chartist movement.
The failure of the April 10th demonstration severely damaged the Chartist movement. In some areas Physical Force Chartism still remained strong. A meeting addressed by Feargus O'Connor in Leicester in 1850 was attended by 20,000 people. There were also large meetings in London and Birmingham. However, the revival of trade reduced the amount of dissatisfaction with the parliamentary system. Chartist candidates did very badly in the 1852 General Election and sales of the Northern Star dropped to 1,200. By the time Feargus O'Connor died in 1855, the Chartist movement had come to an end.