The Great War
Three units formed
 
 1914 
1st / 1st Sussex Yeomanry 2nd / 1st Sussex Yeomanry
 
 1915 
3rd / 1st Sussex Yeomanry
 
 1916 
2nd / 1st Sussex Yeomanry converted to Cyclist and amalgamated with 2nd / 1st Surrey
 
 8th (Surrey and Sussex) Yeomanry Cyclist Regiment 
 
 1917 
1st / 1st Sussex Yeomanry converted to infantry
 
 16th (Sussex Yeomanry) Battalion, The Royal Sussex Regiment 
 
2nd / 1st Sussex Yeomanry resumed separate status as Cyclists
 
 1919 
16th (Sussex Yeomanry) Battalion, The Royal Sussex Regiment disembodied
 
 1920 
2nd / 1st Sussex Yeomanry disbanded
 
Battle Honours awarded to Sussex Yeomanry:
 
  Somme 1918, Bapaume 1918, Hindenburg Line, Epéhy, Pursuit to Mons,    France and 
 
 Flanders 1918,    Gallipoli 1915, Egypt 1916-17, Gaza, Jerusalem, Tell' Asur,    Palestine 
 
Change of arm and re-designated as:
 
 13th Army Brigade, Royal Field Artillery 
 
 389th and 390th Batteries, 98th (Sussex Yeomanry) Brigade, Royal Field Artillery 
 
 1922 
Surrey Yeomanry batteries ( 391st and 392nd ) added with change of title to:
 
 98th (Surrey and Sussex Yeomanry) Brigade, Royal Field Artillery 
 
 98th (Surrey and Sussex Yeomanry, Queen Mary's) (Army) Field Brigade, Royal Artillery 
 
 98th (Surrey and Sussex Yeomanry, Queen Mary's) Army Field Brigade, Royal Artillery 
 
 98th (Surrey and Sussex Yeomanry, Queen Mary's) Army Field Regiment, Royal Artillery 
 
 1939 
On duplication of the Territorial Army, re-designated as:
 
 144th Field Regiment, Royal Artillery 
 
 98th (Surrey and Sussex Yeomanry, Queen Mary's) Field Regiment, Royal Artillery 
 [see Surrey Yeomanry]
 
 144th Field Regiment, Royal Artillery (Surrey and Sussex Yeomanry, Queen Mary's) 
 
 WW2 
Location of operations
 
98th Field Regiment 144th Field Regiment
 
 344th (Susssex Yeomanry) Light Anti-Aircraft and Searchlight Regiment, Royal Artillery 
 
 1950 
Amalgamated without change of title with:
 
605th (Sussex) Heavy Anti-Aircraft Regiment, Royal Artillery
 
258th (Sussex) Heavy Anti-Aircraft Regiment, Royal Artillery
 
313rd (Sussex) Heavy Anti-Aricraft Regiment, Royal Artillery
 
641st (Mixed) Heavy Anti-Aircraft Regiment, Royal Artillery (Sussex)
 
 258th (Sussex Yeomanry) Light Anti-Aircraft Regiment, Royal Artillery 
 
257th (County of Sussex) Field Regiment, Royal Artillery
 
 257th (Sussex Yeomanry) Field Regiment, Royal Artillery 
 
 1967 
Reduced to one Battery designated:
 
 200th (Sussex Yeomanry) Field Battery, Royal Artillery (Volunteers) 
 
 200th (Sussex Yeomanry) Medium Battery, 100th (Eastern) Medium Regiment, 
 
 Royal Artillery (Volunteers) 
 
 200th (Sussex Yeomanry) Medium Battery, 100th (Yeomanry) Medium 
 
 Regiment, Royal Artillery 
 
 200th (Sussex Yeomanry) Field Battery, 100th (Yeomanry) Field Regiment, 
 
To include B Troop from The Surrey Yeomanry (Queen Mary's Regiment),
 
Royal Artillery (Territorials)
 
Two Troops of Sussex Yeomanry formed part of:
 127th (Sussex Yeomanry) Field Squadron, 78th (Fortress) Engineer Regiment, Royal Engineers 
To include a Troop from Surrey Yeomanry and Troops from 39 (City of London) Signal Regiment, Royal Corps of Signals
 
 
 1999 
127
th Field Squadron disbanded
Sussex Yeomanry components are placed in suspended animation (two troops) Surrey Yeomanry and Royal Corps of Signals components (three troops) re-roled and re-designated as:
579th (Bomb Disposal) Squadron, Royal Engineers, 101st (London) Engineer Regiment (Explosive Ordnance Disposal), Royal Engineers
 
 2008 
Two Troops of Sussex Yeomanry component reformed and re-roled as  : 
No. 1 Troop, 579th (Bomb Disposal) Squadron, Royal Engineers, 101st (London) Engineer Regiment (Explosive Ordnance Disposal), Royal Engineers