The first of the new English police recruits arrived in Ireland in March 1920. They were not the type of men who would have been accepted by any police force in normal circumstances. They were young men who had served in the war and had been unable to find work after their demobilisation.

In the post-war economic depression which had struck Britain, unemployment was at a very high level, and few employers were prepared to offer steady jobs to untrained men whose wartime experiences had given them a taste for adventure and had inured them to violence and brutality. Such men eagerly grasped the opportunity to return to the only kind of life they knew or cared about - at the very attractive wages of ten shillings a day.

On their arrival in Ireland it was found that there were not enough of the dark police uniforms to go round, and the missing items of clothing were supplied from khaki army uniforms. Their parti-coloured outfits inspired the nickname 'Black and Tans' and also served to symbolise their anomalous position: they were technically policemen but they acted as a military combat force.

A second armed force known as the Auxiliaries, was created in August 1920 to supplement the Black and Tans. The Auxiliaries were ex-officers and tended to be slightly older, tougher, and more responsible than the Black and Tans. They formed an elite commando-style force; they were paid £1 a day and were allowed considerable freedom of action.

As well as sending the police reinforcements to Ireland, Lloyd George made a number of changes at a higher administrative level which he hoped would make the Dublin Castle government more effective throughout the country. He appointed a new Chief Secretary, Sir Hamar Greenwood, who adopted the policy of allowing the forces of law and order a free hand in their struggle against terrorism. The command of the regular military forces in Ireland was given to General Sir Neville Macready, who was known to favour direct military rule, while another general, H. H. Tudor, was put in charge of the police.

In the second half of 1920 there were about 30,000 regular soldiers in Ireland, as well as 11,000 police (including the Black and Tans and Auxiliaries). The soldiers remained to some extent outside the struggle, partly because the IRA was reluctant to put its strength against experienced professional soldiers, and partly because Lloyd George did not want the army to play an active role in maintaining the peace, since to do so would be to concede full belligerent status to the IRA and thus, in a sense, to recognise the existence of the Irish Republic.

Armed and active IRA members numbered little more than 3,000 at any one time. It remained to be seen whether the reinforced RIC was now of sufficient strength to counter the activities of these men and restore British rule in those areas where it was fast breaking down.

The Black and Tans quickly found that fighting the IRA was a very different matter to fighting the Germans. The First World War had been conducted according to the international rules of war. The opposing armies were very clearly recognisable to one another; they were ranged in trenches which faced each other across a clearly defined no man's land; they advanced or retreated across definite tracts of territory and measured their progress by the amount of land they could defend behind their front line.

But in the kind of guerrilla warfare that now prevailed in Ireland there were no rules; there was no front line or rather the front line was everywhere; the enemy was invisible - but he was everywhere. The IRA wore no uniform (since this would have immediately invited the attention of the numerous superior British forces), and an apparently innocent group of by-standers could suddenly be transformed into a detachment of armed men who could strafe an RIC patrol with gunfire and then slip away quickly and quietly to mingle with the local population.

In conditions like these the Black and Tans' nerves were strained to breaking-point. Their pent-up tensions sometimes exploded in deeds of inhuman savagery. It was quite possible for a harmless man to be shot simply for having his hands in his pockets. Ordinary people throughout the country felt that they were being terrorised by the Black and Tans. Whereas the independently operating Volunteers of 1918-19 had been regarded by many people as something of a nuisance, by the end of 1920 they were seen as the only defenders of public safety against the British forces.