Bernard Montgomery in the context of "Alliance"

The Allied invasion of Italy was the Allied amphibious landing on mainland Italy that took place from 3 September 1943, during the Italian campaign of World War II. The operation was undertaken by General Sir Harold Alexander's 15th Army Group (comprising General Mark W. Clark's American Fifth Army and General Bernard Montgomery's British Eighth Army) and followed the successful Allied invasion of Sicily. A preliminary landing in Calabria (Operation Baytown) took place on 3 September, the main invasion force landed on the west coast of Italy at Salerno on 9 September as part of Operation Avalanche at the same time as a supporting operation at Taranto (Operation Slapstick).

Microwave transmission is the transmission of information by electromagnetic waves with wavelengths in the microwave frequency range of 300 MHz to 300 GHz (1 m - 1 mm wavelength) of the electromagnetic spectrum. Microwave signals are normally limited to the line of sight, so long-distance transmission using these signals requires a series of repeaters forming a microwave relay network. It is possible to use microwave signals in over-the-horizon communications using tropospheric scatter, but such systems are expensive and generally used only in specialist roles.

Although an experimental 40-mile (64 km) microwave telecommunication link across the English Channel was demonstrated in 1931, the development of radar in World War II provided the technology for practical exploitation of microwave communication. During the war, the British Army introduced the Wireless Set No. 10, which used microwave relays to multiplex eight telephone channels over long distances. A link across the English Channel allowed General Bernard Montgomery to remain in continual contact with his group headquarters in London.

Supreme Headquarters Allied Expeditionary Force (SHAEF; /ˈʃeɪf/ SHAYF) was the headquarters of the Supreme Commander, Allied Expeditionary Force (SCAEF), in northwest Europe, from late 1943 until the end of World War II. US General Dwight D. Eisenhower was the commander in SHAEF throughout its existence. The position itself shares a common lineage with Supreme Allied Commander Europe and Atlantic, but they are different titles.

Operation Overlord was the codename for the Battle of Normandy, the Allied operation that launched the successful liberation of German-occupied Western Europe during World War II. The operation was launched on 6 June 1944 (D-Day) with the Normandy landings (Operation Neptune). A 1,200-plane airborne assault preceded an amphibious assault involving more than 5,000 vessels. Nearly 160,000 troops crossed the English Channel on 6 June, and more than two million Allied troops were in France by the end of August.

The decision to undertake cross-channel landings in 1944 was made at the Trident Conference in Washington in May 1943. American General Dwight D. Eisenhower was appointed commander of Supreme Headquarters Allied Expeditionary Force, and British General Bernard Montgomery was named commander of the 21st Army Group, which comprised all the land forces involved in the operation. The Normandy coast in northwestern France was chosen as the site of the landings, with the Americans assigned to land at sectors codenamed Utah and Omaha, the British at Sword and Gold, and the Canadians at Juno. To meet the conditions expected on the Normandy beachhead, special technology was developed, including two artificial ports called Mulberry harbours and an array of specialised tanks nicknamed Hobart's Funnies. In the months leading up to the landings, the Allies conducted Operation Bodyguard, a substantial military deception that used electronic and visual misinformation to mislead the Germans as to the date and location of the main Allied landings. Adolf Hitler placed Field Marshal Erwin Rommel in charge of developing fortifications all along Hitler's proclaimed Atlantic Wall in anticipation of landings in France.