'Gastwirt' was a German unrealised plan for the Abwehr’s Abteilung II department to send two agents of Irish origin to London on a sabotage mission (6 October 1941 onward).

One of the two agents was John Codd, an Irish national captured while serving in the British army in 1940. Limited radio and sabotage training for 'Gastwirt' took place in Germany, but the plan was aborted as a result of the overall collapse of the German programme to train and recruit suitable Irish agents as part of its experiment at Friesack camp in Brandenburg.

At this Stalag XX-A camp a number of Irishmen, who had been serving in the British army and been captured, volunteered for recruitment and selection by the Abwehr’s Abteilung II sabotage and special purpose department and the German army in the 1940/43 period. The camp was later disestablished and its inmates were either despatched to fight on the Eastern Front or interned in concentration camps.

During World War II the Abwehr and the German foreign ministry saw considerable potential in the development of operations on the island of Ireland, in whose southern state there was believed to be considerable animosity to the British, as an easy yet possibly effective way of opening another 'front' against the UK. A number of abortive and indeed a few successful attempts were made to insert Abwehr agents into Ireland with a view to the gathering of intelligence and aiding the anti-British IRA (Irish Republican Army).

The Abwehr’s Abteilung II was a section of German intelligence which, among other duties, was tasked with locating disaffected and anti-authoritarian elements in the nations opposing Germany, and then giving these elements weapons, training and other assistance, and anything else that might reduce these nations' ability to oppose Germany. After the defeat of the French and British forces in north-eastern France during 'Sichelschnitt', in which significant numbers of British troops were captured, the Abwehr that there was merit in examining the possibility of 'turning' such prisoners of war against their former comrades so that they would fight for the German army or serve as Abwehr agents. While it is probable that this was standard procedure for the Abwehr, the decision with regard to Irishmen may have been influenced if not actually prompted by Seán Russell, who was then chief-of-staff of the IRA and had suggested a new force, along the lines of the so-called Irish Brigade (a mere 52 men) of World War I, in the course of meetings with Abwehr and foreign ministry officials in Berlin during the summer of 1940. The Germans then trawled though the prisoners in German camps, and Irish volunteers were transferred Stalag XX-A for induction and training.

The Abwehr decided that recruitment could best be achieved by inviting potential turn-coat PoWs to undertake tasks seen to be equally in the interests of Germany and their own nations. The Abwehr assumed that the cause which would best appeal to Irish nationals was Irish reunification, an end to partition, and the absorption of Northern Ireland into the Irish state. The Abwehr II’s commando unit, Hauptmann Dr Theodor von Hippel’s (from 12 October 1940 Major Hubertus von Aulock’s) Lehr-Regiment 'Brandenburg' zbV 800 was involved in the selection of candidates.

The Germans appreciated that potential recruits putting themselves forward for selection might included moles such as men pretending to be Irish nationalists with orders to report back on the details of the training. To guard against this, each candidate expressing an interest in recruitment was interviewed by a 'Brandenburger' non-commissioned officer named Helmut Clissmann and possibly also by Frank Ryan, a former IRA member who been captured by General Francisco Franco y Bahamonde’s nationalist forces during the Spanish Civil War (1936/39) and whose release from a 30-year prison sentence into the hands of the Abwehr had been organised by the Irish government.

According to Clissmann, the initial December 1940 recruitment pool from the entire Stalag network was five officers and slightly more than 100 men each claiming Irish nationality. The officers made it clear that they would only fight in the event of an invasion of Ireland by British troops (this was being planned as 'Plan W'). When he arrived at Friesack in the spring of 1941, Dr Jupp Hoven, an 'expert' on Irish affairs merely as a result of his time in that country before the war, found a recruiting base of 80 Irish PoWs, but this figure was eventually trimmed to just 10 men whom the Germans felt were sincere in their desire to fight for Germany. In order to keep their agreement to work for the Axis secret from their fellow prisoners, the Germans arranged a 'prison escape' and took the 10 men to Berlin, where there was training camp run by the Abwehr II. Here the men were given instruction in the manufacture of improvised explosives, incendiaries and the like. At a troop training area in western Germany the were also trained in Abwehr radio procedures.

The man selected for 'Gastwirt' was Sergeant John Codd of Dublin, and those for 'Seemewe I' and 'Seemewe II' were Fusilier James Brady of Strokestown and Private Andrew Walsh of Fethard. Cromwell O’Neill, a civilian captured on an interned freighter, was despatched on a spying mission in Northern Ireland but surrendered himself after reaching London.

There were a number of other Irish citizens living or working in Germany at the time, such as the spouses of German civilians or soldiers, drifters, or internees from civilian ships caught in Germany at the outbreak of war. Some, however, did become involved in various activities through sheer circumstance. The Irish intelligence service tried to keep track of these 85 persons.