French Forces of the Interior
The French Forces of the Interior (French: Forces Françaises de l'Intérieur) refers to French resistance fighters in the later stages of World War II. Charles de Gaulle used it as a formal name for the resistance fighters. The change in designation of these groups to FFI occurred as France's status changed from that of an occupied nation to one of a nation being liberated by the Allied armies. As regions of France were liberated, the FFI were more formally organized into light infantry units and served as a valuable manpower addition to regular French forces. In this role, the FFI units manned less active areas of the front lines, allowing regular French army units to practice economy of force measures and mass their troops in decisive areas of the front. Finally, from October 1944 and with the greater part of France liberated, the FFI units were amalgamated into the French regular forces, thus ending the era of the French irregulars in World War II.
After the invasion of Normandy in June 1944, at the request of the French Committee of National Liberation, SHAEF placed about 200,000 resistance fighters under command of General Marie Pierre Koenig, who attempted to unify resistance efforts against the Germans. General Eisenhower confirmed Koenig's command of the FFI on 23 June 1944.
The FFI were mostly composed of resistance fighters who used their own weapons, although many FFI units included former French soldiers. They used civilian clothing and wore an armband with the letters "F.F.I."
According to General Patton, the rapid advance of his army through France would have been impossible without the fighting aid of the FFI. General Patch estimated that from the time of the Mediterranean landings to the arrival of U.S. troops at Dijon, the help given to the operations by the FFI was equivalent to four full divisions.
FFI units seized bridges, began the liberation of villages and towns as Allied units neared, and collected intelligence on German units in the areas entered by the Allied forces, easing the Allied advance through France in August 1944. According to a volume of the U.S. official history of the war,
In Brittany, southern France, and the area of the Loire and Paris, French Resistance forces greatly aided the pursuit to the Seine in August. Specifically, they supported the Third Army in Brittany and the Seventh U.S. and First French Armies in the southern beachhead and the Rhône valley. In the advance to the Seine, the French Forces of the Interior helped protect the southern flank of the Third Army by interfering with enemy railroad and highway movements and enemy telecommunications, by developing open resistance on as wide a scale as possible, by providing tactical intelligence, by preserving installations of value to the Allied forces, and by mopping up bypassed enemy positions.
Political tension 
On 20 June 1944, the French high command decreed the mobilization requirements dating from the start of the war were still in effect, that the FFI units were to be made part of the French Army, and that the FFI was subject to French military law. Assuming control of the French national government after the liberation of Paris, Charles de Gaulle was almost immediately confronted with a challenge to his authority by an FFI flush with triumph as towns and cities were liberated in the wake of the German retreat from France. In late August 1944, there were incidents of FFI misbehavior in the region of Paris, highlighting the risks of having an armed and organized citizenry that suddenly found itself without a mission. De Gaulle believed France required a single decisive leader to restore effective government. The FFI believed they should have a share in national power because of their contribution to the Allied war effort. Subsequently, de Gaulle declared the FFI would be either disbanded or integrated into the French Army, and a series of tense meetings between de Gaulle and FFI leaders in major cities ensued. Despite FFI disenchantment with de Gaulle's methods, in large part they accepted his decision that FFI members would either be amalgamated into the French regular army or return to civilian life.
Subsequent to the liberation of areas where FFI units operated, they often formed battalions and brigades named for their commanders or region of origin (Battalion Oziol, etc.) These FFI units were predominantly of the light infantry class, although some formed light reconnaissance units like the 12th Regiment of Dragoons. Some of these units were used to besiege German troops in still-occupied French ports or to secure France's alpine frontier with Italy, others were used to secure Allied lines of communications in France, and still others were assigned as army reserve units for the use of General de Lattre de Tassigny's French First Army. From October 1944 until March 1945, the FFI units were amalgamated into the French Army in order to regularize the units. Units such as the 49th Infantry Regiment (formerly the FFI Corps Franc Pommiés) and the 3rd Demi-Brigade of Chasseurs (formerly the FFI Alsace-Lorraine Brigade) were constituted in this manner using FFI manpower. Amalgamation was successful in varying degree; the training, tactics and attitudes of the former French Resistance fighters often differed from those of the regular soldiers with whom they served. General De Lattre's comments on this situation are enlightening:
[Traditional military values] were not and could not be the characteristics of the F.F.I. units. Condemned to be born and live in secret, placed outside the law by the enemy and by the enemy's accomplices, they had above all developed the revolutionary military virtues, those of partisans. By force of circumstances the personalities of the leaders had played a determining role and had stamped each maquis with a different brand. . . . To the regiments we had landed the extreme variety of the F.F.I. organizations, their at least peculiar discipline, the differing quality of their groups, the poverty of their equipment, the crying inadequacy of their armament and supplies, the heterogeneity of their officering, the facility with which their superior ranks had been assigned, and in certain cases the ostensibly political nature of their aims, ran counter to the classical military outlook of many officers, some of whom, in reaction, exaggerated their regulation strictness. . . . The part [the FFI] had taken in the fight for liberation not only encouraged them rightly in the wish to retain their individuality; their successes, valued often from a local angle, established in their view the excellence of the military system which circumstances had led them to create and which they intended to substitute for the traditional system, which they considered out-of-date.
Weapons and equipment 
The weapons and equipment of the FFI were highly varied. Because they were not units that the United States had formally agreed to logistically support, they were not eligible to receive the standard U.S. equipment that was provided to French regular army units. Thus, the FFI units often clothed themselves in nonstandard uniforms or uniforms of 1940 vintage. The same condition existed with weapons, with the use of captured German infantry weapons a common practice. Because of the mix of American, British, French, German, and other weapons, the supply of ammunition and spare parts was complicated and often difficult to accomplish. Some heavy armored fighting vehicles were obtained, notably British Cromwell tanks (150 provided by Great Britain) and captured German tanks (44, of which 12 were Panthers). The 12th Regiment of Dragoons received 12 Cavalier tanks among other British equipment in April 1945. In other cases, FFI units used vehicles no longer favored by Allied forces, such as the U.S. M6 Fargo, a light truck with a portee 37 mm antitank gun. Finally, civilian vehicles and practically anything else in running condition were pressed into service and used until they could no longer be maintained.
French strategic asset 
As regions of France were liberated, the FFI provided a ready pool of semi-trained manpower with which France could rebuild the French Army. Estimated to have a strength of 100,000 in June 1944, the strength of the FFI grew rapidly, doubling by July 1944, and reaching 400,000 by October 1944. Although the amalgamation of the FFI was in some cases fraught with political difficulty, it was ultimately successful and allowed France to re-establish a reasonably large army of 1.3 million men by VE Day.
- Harrison, Gordon A., Cross-Channel Attack, pages 206-207. Washington DC: Government Printing Office, 1989, and Pogue, Forrest C., The Supreme Command, page 236. Washington DC: Government Printing Office, 1996.
- "Gripe 17" from the 1945 U.S. forces booklet "112 Gripes about the French"
- Blumenson, Martin. Breakout and Pursuit, pages 363-364 and 674. Washington DC: Government Printing Office, 1989. These are only two examples of many cited in this volume.
- Pogue, Forrest C., The Supreme Command, page 238. Washington DC: Government Printing Office, 1996.
- Vernet, J. Le réarmement et la réorganisation de l'armée de terre Française (1943 - 1946), page 28. Ministere de la Defense, Château de Vincennes, 1980.
- De Lattre de Tassigny, Jean. The History of the French First Army, page 170. London: George Allen and Unwin, Ltd., 1952.
- Vernet, J. Le réarmement et la réorganisation de l'armée de terre Française (1943 - 1946), pages 76-77. Ministere de la Defense, Château de Vincennes, 1980.
- Gaujac, Paul. L'Armée de la Victoire, Vol. IV, page 161. Charles Lavauzelle, Paris, 1986.
- Sumner, Ian. The French Army 1939-45 (2), page 37. Osprey Publishing, London, 1998. ISBN 1-85532-707-4. 200,000 FFI members in October 1944 were believed to be armed.
- Vernet, J. Le réarmement et la réorganisation de l'armée de terre Française (1943 - 1946), pages 86 and 89. Ministere de la Defense, Château de Vincennes, 1980. Vernet lists 10 divisions that were formed with FFI manpower. Ultimately, some 103 light infantry battalions and six labor battalions were formed with FFI personnel prior to VE Day.