Advanced landing ground

Advanced landing grounds (ALGs) were temporary advance airfields constructed by the Allies during World War II during the liberation of Europe. They were built in the UK prior to the invasion and thereafter in northwest Europe from 6 June 1944 to V-E Day, 7 May 1945.

Unlike the permanent airfields built in the United Kingdom and designed for the strategic bombardment of Germany, the tactical combat airfields on the continent were temporary, often improvised airfields to be used by the tactical air forces to support the advancing ground armies engaged on the battlefield. Once the front line moved out of range for the aircraft, the groups and squadrons moved up to newly built ALGs closer to the ground forces and left the ones in the rear for other support uses, or simply abandoned them.

When the Allies invaded Normandy on D-Day, Royal Air Force Airfield Construction Service engineers were among those in the initial assault waves. Their mission was to rapidly construct forward operating airfields, known as advanced landing grounds (ALGs), on the European continent. As the Allied armies advanced across France and into Germany, several hundred airfields were built or rehabilitated for use by the allied air forces.

For security reasons, the airstrips were referred to by a coded number instead of location. In the United Kingdom, USAAF installations were identified by three digit (AAF) numbers ranging from AAF-101 to AAF-925. After D-Day, continental airfields in the European Theater of Operations (ETO) were also assigned coded numbers. American airfields were given A-, Y-, or R-, prefixes and numbered consecutively from 1 to 99. Both "A" and "Y" designated airfields could be found in France, however many "Y" fields would also be in the Netherlands, Belgium and occupied areas of Germany. "R" coded fields were usually located in occupied Germany. British airfields on the continent were also consecutively numbered, but with a B-prefix.

The numbering system for airfields was sequentially assigned as airfields were allocated, not by location or by date of operational use. A-1, Saint Pierre du Mont, was declared operational on 13 June 1944; A-3 Cardonville on 14 June. However A-2, Cricqueville-en-Bessin, was declared operational a few days later on 19 June.

Also many of these airfields had no combat air group or squadron attached to them. They were designed for casualty evacuation and supply transport and consisted of a quickly built runway manned only by a small complement of station personnel with little or no infrastructure other than tents. As the ground forces moved east, wounded would be sent to the airfield to be picked up by C-47s and taken to hospitals in England or other rear areas. Also supplies would be airlifted to the fields and unloaded, to be quickly transported to the front line units. These were normally known as S&E Fields (Supply and Evacuation).

Once completed, airfields were usually utilised by the combat groups or squadrons within a day or so of being declared operational for military use by the IX Engineering command engineers. They would be used for perhaps a few days to a week, to several months, depending on the location, use, and operational requirements. Once the combat units moved up to the next assigned ALG, they could be utilised as S&E Fields, or deconstructed quickly and abandoned, with the land being released back to the landowners or civil authorities in the area.

The mission for constructing ALGs was placed in the hands of the Airfield Construction Service of the RAF Second Tactical Air Force, whilst the USAAF's Ninth Air Force and its specially created engineering arm, the IX Engineer Command, were responsible for ALG's in the US sector of operations. Each aviation engineer battalion in the command (of a total of sixteen) was composed of sufficient men and equipment to quickly construct an airfield or landing ground for a single tactical fighter or bomb group unit.

ALGs were selected in two ways. First, existing enemy military or civilian airfields which were captured as the ground forces advanced were noted by engineers assigned to ground units. Second, engineers noted areas in grid locations where an airfield was desired, that had flat terrain, good land drainage, and where an airfield could be constructed quickly.

Captured airfields could be restored for use as advanced landing field in one to three days depending upon the amount of damage and the number of mines and booby traps encountered.

Dry-weather advanced landing fields were constructed by a single battalion at a favourable site in flat terrain in one to three days, including time for reconnaissance. At less favourable sites, where more clearing and grading were required, or all-weather fields which also needed additional infrastructure, the time varied from three to ten days.

ALGs were equipped with an access road that was connected to the existing road infrastructure; a dump for supplies, ammunition, and gasoline drums, along with a drinkable water and a minimal electrical grid for communications and station lighting. Tents were used for billeting and also for support facilities. Time was the all-important factor and ALGs serve its purpose if available for only a few days. As the forward area became the rear area, an advanced landing field could be improved for medium bomber use, but initially they primarily served fighter and transport groups.

Based on the experience obtained in the North African and Italian campaigns, fighter groups required an airfield 120 feet x 3600 feet long, and fighter-bomber groups required fields 120 feet x 5000 feet long. Medium bomb groups required 120 feet x 6000 feet runways.

Instead of using rough, unimproved dirt strips, engineers used surfacing material necessary to strengthen the soil to support the weight of the aircraft and as a measure of insurance against the wet weather. Airfields were initially single runway landing strips which were laid down east–west (09/27) unless local conditions dictated a different runway direction.

• Sommerfeld Tracking

ALGs laid in the UK were of Sommerfeld Tracking, a form of stiffened steel wire mesh.

• Square-mesh track (SMT)

The surfacing material selected for the building of advanced landing grounds during the first weeks after the Normandy invasion was known as square-mesh track (SMT). SMT, a British development, was material composed of heavy wire joined in three-inch squares. It was chosen over other surfacing materials because it was very lightweight, allowing sufficient quantities to be transported across the English channel on over-tasked landing craft. Easily workable, a SMT landing mat for fighters could be laid like a carpet in about one week.

• Prefabricated Hessian (PBS)

After the initial batch of airfields was completed using SMT, the Army aviation engineers switched almost exclusively to another surfacing material known as prefabricated hessian (burlap) surfacing (PBS). Light and easily transportable, PBS did not create the dust problem encountered with SMT fields. Made of an asphalt-impregnated jute delivered in rolls 300 feet in length and 36 inches or 43 inches in width, PBS was laid in overlapping layers to produce a dust-free fair weather surface. It was also common to build airstrips using both SMT and PBS, laying SMT on top.

• Pierced steel plank (PSP)

To provide an all season durable airfield for the RAF's 2TAF and the USAF Ninth Air Force's medium and light bombers, a third type of surfacing material known as pierced steel plank (PSP), or Marsden Matting was introduced on the Normandy bridgehead in July 1944. It consisted of 10-foot-long (3.0 m), 15-inch-wide (380 mm) steel planks joined together and laid perpendicular to the line of flight. Long used in other theatres, PSP would have been ideal for all airfields on the continent, but its limited availability and greater weight made this impractical. Moreover, because of supply problems, construction of even a PSP fighter-bomber field could take a month or longer, while similar PBS and SMT fields could be constructed in two weeks and one week, respectively.

In addition, sod and earth runways were built for emergency landing strips (ELS) and refuelling and rearming strips (R&R). Captured airfields contained a wide variety of runways, most commonly asphalt; concrete; macadam or tar-penetrated macadam.

There were five main types of airfields built by the USAAF combat engineers on the continent. These were:

• Emergency Landing Strips (ELS)

Consisted of a rough, graded runway approximately 2000 feet long to provide a place for emergency belly-landings of damaged aircraft.^{[page needed]}

• Supply and Evacuation (S&E)

Usually a rough graded runway near the front line or an airfield in the rear that was used by C-47s for transport of casualties to the rear, or delivery of supplies and munitions to the front line.^{[page needed]}

• Refueling and Rearming (R&R)

Consisted of a runway and an aircraft marshalling area on each end of the runway. It was designed to provide an airfield near the front lines upon which aircraft based in rear areas could land, be refuelled and rearmed, and take off again on a mission without having to return to their home field in the rear. Also could be used for dispersal or for when services other than refuelling or rearming was required. These airfields could be expanded into advance landing grounds by the addition of dispersal and other station facilities. Generally if an R&R strip was built, it would be sited wherever possible with a view to further expand it later into an ALG.^{[page needed]}

• Advanced landing grounds (ALG)

An advanced landing ground could be constructed as such from the beginning or by development from an R&R Strip by the addition of dispersal facilities, expansion of the road network and other additions to the station and technical area in order for it to be used over an extended period of time.^{[page needed]}

• Tactical air depots (TAD)

A number of ALGs were expanded into tactical air depots by the addition of hangars, shops, more dispersal hardstands, roads, and other facilities. Some were developed from the beginning.^{[page needed]}

Four main designations were given to ALGs on the European Continent:

• "A" ALGs were located in France. They were constructed and used by Ninth Air Force units during the Invasion of Normandy (6 June – Mid July 1944) and during Operation Cobra, the break-out from Normandy, starting on 25 July 1944 until 25 August 1944. Those in Normandy were mostly decommissioned after their combat use, however others in Central France were used in various non-combat roles until the end of the war.
• "B" ALGs were built by American or British combat engineers for Royal Air Force use. Some of these were also used by USAAF Troop Carrier Groups and Command and Control organisations.
• "Y" ALGs were initially located in Southeastern France, built by Twelfth Air Force engineers as part of Operation Dragoon, the invasion of Southern France. Initially uncoded, they were given "Y" designations when they came under IX Engineering Command control in late 1944. ALGs were also coded "Y" in Northeastern France, Belgium; The Netherlands and Occupied Germany, after "A" coding reached 99 November 1944.
• "R" ALGs were located in Occupied Germany. Many more were constructed than are listed here, consisting primarily of Supply and Evacuation airfields either laid down quickly in agricultural areas or on captured Luftwaffe airfields. "R" coding began after Y-coding reached 99 in April 1945.

An unforeseen development was the extraordinary demand for transport, supply, and evacuation fields as the Allied armies pushed past Paris toward the German frontier. In late 1944, supplies could not keep pace with U.S. General Dwight D. Eisenhower's forces, and to help lessen the supply shortage airfields for C-47 Skytrain cargo planes became a priority. Bringing in ammunition of all types and especially gasoline on the trip to the ALGs on the continent, the C-47s on the return trip evacuated wounded to the rear.

By 15 September 1944, IX Engineer Command had placed over eighty ALG airfields in operation, while British engineers had constructed 76 airfields in their zone. In Southern France, another twenty or so fields had been built by American engineers from Twelfth Air Force from the Mediterranean Theater of Operations (MTO). In October these uncoded airfields were assigned to the ETO and given ALG code numbers.

The stabilisation of the front lines in the Netherlands, Belgium, and eastern France in mid-September 1944, which would last into the new year, allowed aviation engineers a chance to reorganise and prepare for the upcoming winter season. As expected, they could not build new PHS and SMI airstrips during the fall rain and winter snow seasons because of the moist ground. Besides concrete, the American-made PSP was the only available surfacing material that could be laid down during this inclement weather in Europe.

To keep the supply lines open, selected airfields in Belgium and France were therefore "winterized" with PSP. Because of the limited supply of PSP, however, only a limited number of airfields could be winterised, making it necessary to base two group sized units per airfield. But sufficient fighter-bomber and medium bomber airfields were completed that winter to ensure 2TAF and Ninth Air Force aircraft could continue flying combat missions.

The major problem affecting airfield construction in early 1945 was not the surprise German Ardennes counteroffensive (which caused the abandonment of only one airfield – Y-39, Haguenau). Rather, an early February thaw threatened to make airfields inoperable due to the mud and water. Using local civilian labour, engineers performed extensive maintenance on the threatened airfields and successfully resolved the crisis.

The renewed allied offensive in early 1945, following the Battle of the Bulge, was supported in earnest by the building of tactical airfields in occupied Germany. Trier (Y-57), became the first operational tactical American airfield on German soil on 10 March 1945. When a crossing over the Rhine River was spearheaded at Remagen, Germany, a supply and evacuation strip was quickly set up to support the bridgehead. As Allied tank columns struck out rapidly into the heartland of Germany, the airfield "clutches" of the Ninth Air Force's tactical air commands moved east of the Rhine river within range of virtually any target in Germany.

Scores of former Luftwaffe sod and hard surfaced airfields were captured in the lightning advance through Central Germany, virtually undamaged, lessening the requirement for SMT, PHS, and PSP prefabricated surfacing. The relative lack of German military opposition in late March, April and May 1945 lessened the need for close air support and produced a greater demand for supply airstrips to keep the offensive moving. Every opportunity was used to clear captured German airfields for use along the armies' route, allowing C-47s and other transports to land with food, gas, and ammunition. The supply effort received top airfield priority. By V-E Day, 9 May 1945, 76 of the 126 airfields made operational east of the Rhine river were strictly supply and evacuation fields.

USAAF Engineers constructed or rehabilitated over 280 continental airfields in the ETO from D-Day to V-E Day. In the summer months that followed, a few new airfields were constructed, but the vast majority were abandoned and turned over to local landowners or civil governments. Throughout Western Europe, as well as the airfields built by Twelfth and Fifteenth Air Forces in the MTO, a significant number were developed into permanent, civilian airports or NATO military bases after the war.

The airfield coding system remained in effect until after the Japanese surrender in the Pacific, when, on 14 September 1945, the system was officially discontinued. Thereafter, airfields were referenced by their geographic name.

Only active combat ALGs are shown. Dedicated S&E, Liaison, Transport, and other non-combat airfields are not listed. Runway types are listed as follows:

Runway dimensions are in feet.

Advanced landing grounds were built in Kent during 1943 and 1944 for several reasons. The first being a requirement by the allies to station short-range fighters close to the English Channel coast so missions could be undertaken to attack enemy coastal fortifications; road and rail networks and other military targets in Occupied France prior to the invasion of Normandy. Also construction of the ALGs provided necessary engineering and construction training as well as providing practical experience in the development of forward airfields which would be necessary on the continent after the invasion. The ALGs laid down in Kent had two runways, while the ones laid down in France after the invasion generally had only one strip laid down east–west for speed of construction

Due to their temporary nature, the airfields were torn up and salvageable components were re-used on new ALGs in France after the assigned units were moved forward onto French ALGs after the invasion of Normandy.

Airfields in France used in support of the invasion and establishment of Allied forces in Normandy, France, during Operation Overlord and the immediate aftermath, 6 June – 24 July 1944

• A-9 Le Molay-Littry (Le Molay), France

Located: 49°15′42″N 000°53′29″W / 49.26167°N 0.89139°W / 49.26167; -0.89139 (A-9 Le Molay-Littry)

Opened: 30 June 1944 Closed: 5 October 1944

Runway: 4000x120, SMT (04/22)

Used by:^{[page needed]}

67th Tactical Reconnaissance Group, July – August 1944 (F-4/P-38; F-5/P-51)

12th Tactical Reconnaissance Squadron, 5 July – 11 August 1944 (F-5/P-51)

• A-11 Saint-Lambert, France

Located: 49°17′01″N 001°05′54″W / 49.28361°N 1.09833°W / 49.28361; -1.09833 (A-11 Saint-Lambert)

Opened: 5 August 1944 Closed: 11 September 1944

Runway: 5000x120, PHS (05/23)

Used by:

474th Fighter Group, 6–29 August 1944 (P-38)

• A-12 Lignerolles, France

Located: 49°10′32″N 000°47′24″W / 49.17556°N 0.79000°W / 49.17556; -0.79000 (A-12 Lignerolles) (abandoned)

Opened: 18 July 1944 Closed: 4 November 1944

Runway: 5000x120, PHS (07/25)

Used by:^{[page needed]}

362d Fighter Group, 2 July – 10 August 1944 (P-47)

365th Fighter Group, 15 August – 3 September 1944 (P-47)

• A-13 Tour-en-Bessin, France

Located: 49°17′27″N 000°44′59″W / 49.29083°N 0.74972°W / 49.29083; -0.74972 (A-13 Tour-en-Bessin)

Opened: 28 July 1944 Closed: 2 December 1944

Runway 1: 5000x120, PSP (12/30)

Runway 2: 5000x120, PSP (01/19)

Used by:^{[page needed]}

373d Fighter Group, 19 July – 19 August 1944 (P-47)

406th Fighter Group, 5–17 August 1944 (P-47)

394th Bombardment Group, 25 August – 18 September 1944 (Martin B-26 Marauder)

• A-21 Saint-Laurent-sur-Mer, France

Located: 49°21′49″N 000°52′26″W / 49.36361°N 0.87389°W / 49.36361; -0.87389 (A-21 Saint-Laurent-sur-Mer)

Opened: 8 June – 25 August 1944

Runway: 3400x120, ETH (11/28)

Used as: Casualty evacuation and transport Airfield (IX Service Command)

• A-22 Colleville-sur-Mer, France

Located: 49°21′15″N 000°49′41″W / 49.35417°N 0.82806°W / 49.35417; -0.82806 (A-22 Colleville-sur-Mer)

Opened: 13 July – 4 November 1944

Runway: 3750x120, PBS (09/27)

Used as: Transport Airfield

The US marks the "Northern France Campaign" from the break-out following the invasion of Normandy to September 1944.

Airfields captured or established to support combat operations during the Western Allied Invasion of Germany (1 February – 8 May 1945). This section lists those used during the war; ones used during the occupation period of Germany are listed in the Army of Occupation ALGs section.

ALGs used by American forces in Occupied Germany and Austria after the German surrender on 7 May 1945. Primarily used for storage of captured German weapons, aircraft and equipment before their destruction. Also for garrisons of US Army or US Army Air Force personnel.