The UK government stated that 700 people from the UK went to fight in Syria. At least half of these people returned to the UK.
The government is concerned that the UK nationals who have joined ISIS in Syria and Iraq returned to the UK and are ready attack.
Home Office minister James Brokenshire stated that 700 people from the UK are considered a threat to British society.
Police consider those who have returned to Britain a security risk. From the beginning of 2015, there were more than 150 ISIS-related attacks around the world.
So far, six terror attacks on Britain were prevented in 2015.
Defence Secretary Michael Fallon warned that other terror attacks on the streets of Britain are planned by several ISIS militants in Syria. These attacks are planned to happen on major public events and it is possible that members of the armed forces will be attacked.
He added that the government must deal with such crisis, identify responsible people and stop those attacks.
During a military strike conducted by the UK in a foreign country, Briton Reyaad Khan, along with two other ISIS militants, was killed in an RAF drone strike.
He added that it was the only way to stop Khan from overseeing terror attacks around the world. This action is considered a defense against an armed attack planned by these terrorists.