Before the last shots of the Polish 1939 Campaign were fired, the nucleus of the future resistance organisation, the Home Army was being put into place in Warsaw. At the time it was called Service for the Victory of Poland. Soon replaced by the Union of Armed Combat in November 1939, it developed into a formidable fighting machine. In February 1942 it was renamed the Home Army (Armia Krajowa). From the outset it was recognised that one of the major tasks of the Home Army was to organise an efficient intelligence gathering service both for its own needs and that of the allied war effort. Built partially on the pre war structure of Polish intelligence networks, expanded and developed during the occupation, the Home Army Intelligence Service become the chief source of information for the allies about the eastern front. The important role of intelligence was recognised by the Commandant in Chief of the Union of Armed Combat, Gen. K. Sosnkowski in his first instruction of January 1940 directed to the Commanding Officer Polish resistance, in which the first point was entirely devoted to the organisation of the intelligence service.

The Intelligence Bureau of GHQ Home Army underwent various structural changes until it finally took permanent shape in 1942. Its organisation in many respects mirrored the organisation of the Directorate of Military Intelligence of the Polish General Staff in London. Though not directly subordinated to it, it was in effect an extended arm of the Polish Military Intelligence centre based at Polish GHQ in the Rubens Hotel in London.

Reflecting the organisation of the Polish General Staff, the Home Army Intelligence Service was established on strict organisational lines. Throughout the occupation its chiefs were: Major Wacław Berka “Brodowicz” (1939 – 1942), Lt Col. Marian Drobik “Dzięcioł” (1942 – 1943), Co. Kazimierz Iranek-Osmecki "Makary" (1943 – 1944) and Lt Col Bohdan Zielinski "Tytus" (1944 – 1945).

The Intelligence Bureau of GHQ Home Army was organised into the following departments: Secretariat, Department of Propaganda, Department of Military Analysis, Department of Industrial Intelligence Analysis, Department of Internal Communications, Department of Finance and Welfare, the Intelligence Department and the Department of Legalisation and Technology, Counter-Intelligence Department, and Section 666, which was responsible for direct communications via Berlin – Paris – to Spain. By far the most important of the above was the Intelligence Department code-named "Stragan". It was divided into Section "West" responsible for the Reich, Section "North" responsible for Pomerania and East Prussia, Section "South" which included all territories south of Warsaw as far as Vienna, Section "East" – for all territories east of Warsaw. This set up lasted until 1942 when it was broken up by German counterintelligence. Following its reconstruction the Army Intelligence Service was divided into three distinct sections. The first was the Section responsible for the General Gouvernment code-named "52-kk" later "Arkadiusz". The second was Section "East" ("WW-72", then "Pralnia"). The last one was Section "West" ("Lombard").

Thus the Home Army Intelligence network held sway not only in occupied Poland but also well into the Reich, the USSR and countries south of Poland, allied to Germany. It soon transpired that for the Allies this was the main source of intelligence information. For instance it was not until 1942 that the British Intelligence Service could claim to have rebuilt – at least in part, their network in Germany. To that date and effectively until the end of the war their main source of information was the Polish Intelligence Service of the Home Army as far as information concerning Germany and the eastern front was concerned.

The British Intelligence Service quickly realised the potential of their ally’s service. It was not long before a formal agreement between them and Polish Intelligence was reached. A line of communications and procedure were established by which the British Intelligence Service requested specific information from their Polish allies. The Intelligence Bureau of the Polish General Staff passed on the requests to the Special Bureau of the Polish General Staff responsible for communications with the Home Army in occupied Poland. They in turn passed on the request to the GHQ Home Army in Warsaw. There the intelligence service using its various networks gathered the sought for information which was analysed in their Studies Department before being send back to Polish GHQ in London. The Special Bureau transferred it to the Intelligence Bureau which passed it on to the British IS Liaison Section before it was distributed according to interest i.e.: Military Intelligence, Air Intelligence, Naval Intelligence, Ministry of Economic Warfare etc. Throughout the war Home Army Intelligence supplied the Allies with over 25,000 reports.

The Intelligence Service of the Home Army supplied the allies with regular and continuous information regarding the: ordre de bataillle of German forces on the eastern front (army group GHQs, army HQ’s, armies, corps and divisions including commanding officers, identification markings, areas of concentration, numbers etc.); troop transports between the eastern and western fronts; identification and battle order of Luftwaffe units, armament and industrial production especially of synthetic fuels, movement of units of the Kriegsmarine in German and Baltic ports, U-boat construction, tank and armoured vehicle construction and innovations, industrial espionage in its widest sense, morale of Germen troops and civilian population. Thanks to the professionalism of the Army Intelligence Service over and above of the constant flow of information of the above-mentioned type, it supplied the allies with information regarding the build up of German forces on the eastern front in preparation of the attack on the USSR. This information was duly passed on to Moscow which chose to ignore it, at its own peril. The other major coup of Home Army Intelligence was the acquiring of information regarding German’s secret weapons the V1 and V2 rockets. Regarding the former, Home Army Intelligence supplied information about the activities in Peenemünde which was crucial in the British decision to mount a bombing operation in August 1943. The following year Polish Intelligence supplied the allies with complete instructions, analysis and full rocket parts of the V2 which enabled them to prepare an adequate defence of the British isles.

It is hardly surprising that the German forces of occupation concentrated upon trying to infiltrate and smash the Home Army Intelligence Service. Though they had undoubted success in as much that senior officer of the service were found, arrested and murdered (including the Home Army IS’s two first chiefs) the network was soon re-established and functioning at full strength.

The British Intelligence service was cogniscent of the service being rendered to the allied cause by Home Army IS and duly expressed its appreciation in the evaluation of individual reports as well as of the periodical ones, such as that of July 1942 in which the British service paid homage to the Home Army IS saying: