The 1st battalion was also part of the Nile Expedition, an unsuccessful attempt to save General Charles Gordon and his garrison at Khartoum during the Mahdist War.

Twenty men of the regiment, led by Lieutenant Lionel Trafford, constituted the advanced party which marched towards Khartoum.

[5] The 2nd Battalion was stationed at Malta from 1882, then moved to India in 1885 and took part in the Hazara Expedition in 1888 and the North-West Frontier campaign 1897–1898.

[6][7] When the Second Boer War required more troops to reinforce British forces in South Africa, the 1st Battalion was sent there in February 1900, and fought at the Battle of Doornkop in May 1900.

[8] A memorial to the fallen of the Second Boer War, incorporating a sculpture by Charles Leonard Hartwell titled "The Bugler", is at Regency Square, Brighton.

The Sergeant Bugler sounded the charge of The Royal Sussex that swept The Boers from their formidable position at Doornkop.

[10] A silver reduction copy is also held by The 2nd Battalion Princess of Wales's Royal Regiment Officers' Mess.

[13] Following the end of the war in South Africa, the 1st battalion transferred to India, where they were stationed at Sitapur in Bengal Presidency.

[18] The 2nd Battalion landed in France as part of 2nd Brigade in the 1st Division in August 1914 and fought through the war on the Western Front.

[19] During the Battle of Loos in September 1915 Sergeant Harry Wells was awarded a posthumous Victoria Cross, when the battalion took part in an attack.

[17] The 1/5th (Cinque Ports) Battalion landed in France as Army Troops in early 1915, seeing action from the Battle of Aubers Ridge with 1st Division in May 1915.

It later joined 48th (South Midland) Division as divisional pioneers, seeing action at the Somme and Ypres[17][21] before moving to Italy in November 1917.

[17] The 1/6th (Cyclist) Battalion remained on coast defence duties in England and Ireland for the whole war, but the 2/6th was converted to infantry and saw action with 16th Indian Division in Waziristan in 1917–19.

[24] Edmund Blunden, a second lieutenant in the 11th Battalion, wrote an excellent account of his experiences in his memoirs, Undertones of War (1928).

[4] After the war, St George's Chapel, in Chichester Cathedral, was restored and furnished as a memorial to the fallen of the Royal Sussex Regiment.

[4] In late 1944 the battalion was shipped across to Greece with Lieutenant-General Ronald Scobie and his III Corps, remaining there until 1946 to help calm the Greek Civil War after the German withdrawal.

The brigade participated in Operation Slapstick, an amphibious landing on the Italian port of Taranto, as part of the Allied invasion of Italy.

Then returning to England, the battalion then fought at Arnhem during the disastrous Operation Market Garden in September 1944 with the rest of the 1st Airborne Division.