A few hours before the UK’s first air strikes on Islamic State targets in Iraq, the home secretary, Theresa May, warned the Tory party conference that IS could become the "world’s first truly terrorist state".

May said that IS could realise the “often-prophesied” threat of attacking western enemies with chemical and nuclear weapons. Interesting because, as this conflict has approached, the government has been using the same techniques and devices of propaganda and persuasion that were brought out to justify the Iraq war of 2003, the removal of Colonel Gaddafi in 2011 and the proposed attacks on the Assad regime in Syria in 2013.

If you look back at recent conflicts, and those in the Middle East in particular, the same arguments are made. There is essentially a five-point plan that can be used to justify foreign intervention of most kinds.

Step 1. Highlight atrocities

If you are to claim the moral high ground, the first thing to do is show that your adversary is despotic and deranged. For British governments and the media, that has long meant using atrocity propaganda.

At the beginning of the Gulf War in 1991, we were falsely told that Iraqi soldiers had emptied babies out of incubators in Kuwaiti hospitals and left them to die. In Kosovo in 1999, Tony Blair spoke of hearing “first-hand of women raped, of children watching their fathers dragged away to be shot”. In 2003, Blair spoke of the thousands of children dying every year in Iraq and Saddam’s torture chambers. Now, IS is highlighting its own barbarity in online videos and the case for action on this count hardly has to be made.

Step 2. Communicate moral obligation

Having established these terrible circumstances, it is necessary to demonstrate the moral certainty of the mission. In 2011, Muammar Gaddafi, like Saddam before him, was murdering “his own people”. The consistent line from the US, the UK and France back then was humanitarian. At a stroke we have the basic elements of war propaganda: the enemy is evil and to do nothing in the face of such evil would amount to dereliction of moral duty.

David Cameron and Barack Obama took a predictably similar view. In a nationally televised address, Obama said, “to brush aside America’s responsibility as a leader and — more profoundly — our responsibilities to our fellow human beings under such circumstances would have been a betrayal of who we are … some nations may be able to turn a blind eye to atrocities in other countries. The United States of America is different”.

Here is a repetition of themes and ideas which have been the feature of war propaganda from time immemorial: this is the enemy, they do terrible things. We must stop them. If we do not, then we are no better than them and evil will prosper.

Step 3. Deny enemy’s humanity

Aldous Huxley wrote that: “the propagandist’s purpose is to make one set of people forget that certain other sets of people are human”. On September 25, Cameron told the UN General Assembly that the jihadi’s of IS were “psychopathic, murderous, brutal”. He said: “we are facing an evil against which the whole world must unite. And, as ever in the cause of freedom, democracy and justice, Britain will play its part." Here we get the explicit sense of civilisation versus savagery, of human versus animal. Good against evil. Simple binary oppositions, again narrative patterns we can all understand.

Step 4. Say intervention is for the people

On the eve of war in 2003, Tony Blair spoke to the nation outlining the need for action. For the people of Iraq, the removal of Saddam would be "a blessing”. When bombing began in Libya in 2011, NATO stated that the purpose of Operation Unified Protector was to protect civilians and civilian-populated areas under threat of attack from Gaddafi.

There was no military activity in Syria last year but the language was familiar. On the August 27, the UK government sought backing from the UN Security Council: "for all necessary measures to protect civilians". The US secretary of state, John Kerry, stated that the images of human suffering could not be ignored. He said: “All peoples, in all nations who believe in the cause of our common humanity must stand up to ensure there is accountability for the use of chemical weapons.”

Cameron has been quite clear that military intervention was for the good of Iraq and at the country’s own asking: “We are acting [in Iraq] at the request of a sovereign state … I have said this in the house before: it is a legal base if you are averting a humanitarian catastrophe then you can act. Let me be clear.”

Step 5. Raise threat to national security

This brings us to May’s comments at the beginning of this article. If a government can also illustrate that this far-away, evil regime constitutes a threat to national security, the danger becomes localised. This tactic was utilised with various degrees of success in the run-up to the Iraq War in 2003. In January of that year, for example, the press carried reports that the police had foiled a terrorist ring’s attempt to launch a chemical attack in Britain using the deadly poison Ricin. Blair stated that the find showed: “This danger is present and real and with us now – and its potential is huge.”

In 2013, the danger was from rogue states and banned weapons. Arguing for intervention in Syria, the then foreign secretary, William Hague, said: “We cannot permit our own security to be undermined by the creeping normalisation of the use of weapons that the world has spent decades trying to control and eradicate.”

Now, according to Hague, ISIS has the UK in its sights – he told the Daily Telegraph on the September 28 that without military action, ISIS “would come to hit us very quickly –indeed there have already been plots."

For Cameron, ISIS constitutes a ”clear and present danger“ to the UK which must be defeated promptly because: "If we do not act to stem the onslaught of this exceptionally dangerous terrorist movement, it will only grow stronger until it can target us on the streets of Britain.”

The point of this article has not been to understate the threat of ISIS or to diminish the horror of its actions. But history has a way of repeating itself – as do the statesman and women who feature in it, and take their countries into wars that hindsight often suggests they shouldn’t have.

However much technology and times may change, the techniques of propaganda and persuasion remain largely the same.