ISIS
ISIS took root in the new era created in Iraq after the Americans took control of the country in 2003. The Second Gulf War led to the overthrow of Saddam Hussein’s regime, the dismantling of the Iraqi army and the destruction of the existing governmental structure.
The group seized Mosul, Iraq, last June, and already rules an area larger than the United Kingdom. Abu Bakr al-Baghdadi has been its leader since May 2010, but until last summer, his most recent known appearance on film was a grainy mug shot from a stay in U.S. captivity at Camp Bucca during the occupation of Iraq. Then, on July 5 of last year, he stepped into the pulpit of the Great Mosque of al-Nuri in Mosul, to deliver a Ramadan sermon as the first caliph in generations—upgrading his resolution from grainy to high-definition, and his position from hunted guerrilla to commander of all Muslims. The inflow of jihadists that followed, from around the world, was unprecedented in its pace and volume, and is continuing.

IRA (Irish republican army)
The Irish Republican Army (IRA) is any of several armed movements in Ireland in the 20th and 21st centuries dedicated to Irish republicanism, and Irish nationalism, the belief that all of Ireland should be an independent republic.
The IRA which traces its roots to Catholic Irish nationalism in the early 1900s, was considered by many to be a terrorist organization because of certain tactics like bombings and assassinations it used to oppose British rule in Ireland.
The name IRA has been in use since the organization was founded in 1921. From 1969 through 1997, the IRA splintered into a number of organizations, all called the IRA.
They included:
The Official IRA (OIRA)
The Provisional IRA(PIRA)
The Real IRA (RIRA), and Continuity IRA (CIRA).

Methods used by UK public services to counter both national and international terrorism
The Command was formed in October 2006, with the merger of its two predecessor units; the Anti-Terrorist Branch (SO13) and Special Branch (SO12). It continues their legacy of expertise and brings together intelligence, operations and investigations functions. It also engages with a range of partners to prevent terrorist related activity, including the British Security Service and Secret Intelligence Service.

The Counter Terrorism Command operates against the threat of terrorism at a local, national, and international level and supports the national Counter Terrorism Network and the Senior National Co-ordinator Counter Terrorism. In addition to this core counter-terrorism function the Command has a