The regiment was expanded to three battalions during the Second World War, and served in France, North Africa, Tunisia, Italy and Western Europe.

In the post war period, the regiment was reduced to a single battalion and saw service in Palestine, Egypt, West Germany, Aden, Northern Ireland, and Cyprus.

In May 1940 at the Battle of Arras, the Welsh Guards gained their second Victoria Cross by Lieutenant Christopher Furness, who was subsequently killed in action.

The two battalions worked closely, being the first troops to re-enter Brussels on 3 September 1944 after an advance of 100 miles in one day in what was described as 'an armoured lash unequalled for speed in this or any other war' led by Major-General Sir Allan Henry Adair, the divisional commander.

The Welsh Guards returned home the following year and soon after deployed to the British-controlled Suez Canal Zone (SEZ) in Egypt.

The following year the Welsh Guards were dispatched to the province again, and during this period lost Guardsman David Roberts in a landmine explosion.

[9] Between October 1975 and March 1976 the Welsh Guards were part of the British contingent of the United Nations force deployed to Cyprus in the aftermath of the Turkish invasion of the island in 1974.

[10] In 1977 the regiment arrived in West Berlin again, and then in 1979 once more in the midst of the volatile situation in Northern Ireland, they lost Guardsman Paul Fryer to a booby-trap bomb.

On 9 July 1981, Daniel Barrett, aged 15 years, was sitting on the garden wall of his home in Havana Court, Ardoyne, North Belfast, when he was shot dead by a soldier from the Welsh Guards.

[12] On 13-14 June, the remainder of the battalion, reinforced by two companies of Royal Marines from 40 Commando, were given the objective of capturing Sapper Hill in the final stages of the Battle of Mount Tumbledown.

Following a firefight at their helicopter landing zone, the force moved on to Sapper Hill but found it abandoned, thus taking the last defensible position before Stanley.

In 1989 The Welsh Guards conducted a six-month operational roulement Battalion tour of Belize from April to October 1989 and in 1992 arrived in Northern Ireland for a two-year deployment as part of 8th Infantry Brigade.

[15] On 6 September 1997, 12 Guardsmen of the Welsh Guards led by the adjutant of the 1st Battalion, "The Prince of Wales" Company, Captain Richard Williams MC, hero in 1993 of the Khmer Rouge incident in which he was captured defending civilians in Cambodia,[16] were pulled from security patrols in South Armagh, Northern Ireland and together with members of the King's Troop, Royal Horse Artillery escorted the casket of Diana, Princess of Wales, from Kensington Palace to Westminster Abbey.

[17] In 2002, the regiment arrived in Bosnia as part of SFOR, a NATO-led force intended to ensure peace and stability in the Balkan nation.

It was involved in Operation Fresco, the British armed forces response to the firefighters strike; the Welsh Guards covered the Midlands area, primarily in Birmingham using the antiquated Army "Green Goddess" fire engines.

In November 2007, the regiment deployed to Belize at short notice to take part in jungle warfare training; they returned just before Christmas.

[21] In 2008, the Welsh Guards moved from London to Lille Barracks in Aldershot, in preparation for deployment on Operation Herrick 10 in Afghanistan.

[23] On 1 July 2009, Lieutenant-Colonel Rupert Thorneloe MBE was killed along with Trooper Joshua Hammond of the 2nd Royal Tank Regiment, following the detonation of an IED in Afghanistan under their BvS 10 Viking during Operation Panther's Claw.

[24] As a result of the Army 2020 Refine reforms, the battalion moved to Combermere Barracks which was the former home to the armoured regiment of the Household Cavalry.

[54] The Welsh Guards have been awarded the following battle honours:[55] Loos, Somme 1916 '18, Ginchy, Flers Courcelette, Morval, Ypres 1917, Pilckem, Poelcappelle, Passchendaele, Cambrai 1917 '18, Bapaume 1918, Arras 1918, Albert 1918, Drocourt-Quéant, Hindenburg Line, Havrincourt, Canal Du Nord, Selle, Sambre, France and Flanders 1915–18 Defence of Arras, Boulogne 1940, St Omer-La Bassée, Bourguébus Ridge, Cagny, Mont Pincon, Brussels, Hechtel, Nederrijn, Rhineland, Lingen, North-West Europe 1940 '44–45, Fondouk, Djebel el Rhorab, Tunis, Hammam Lif, North Africa 1943, Monte Ornito, Liri Valley, Monte Piccolo, Capture of Perugia, Arezzo, Advance to Florence, Gothic Line, Battaglia, Italy 1944–45 Falkland Islands 1982