Military units and formations disestablished in 1921

The 3rd Light Horse Brigade was a mounted infantry brigade of the Australian Imperial Force (AIF), which served in the Middle Eastern theatre of World War I. The brigade was initially formed as a part-time militia formation in the early 1900s in Victoria. In 1914, the brigade was re-constituted as part of the AIF. The brigade first saw action while serving with the Australian and New Zealand Army Corps during the Gallipoli campaign where they were noted for their attack during the Battle of the Nek. After being withdrawn to Egypt in February 1916 they were involved in the Sinai and Palestine Campaign until the end of the war. They were attached to a number of different formations being part of the Anzac Mounted Division in March 1916 and the Australian Mounted Division in June 1917, who they remained with until the end of the war. After the war, the AIF light horse regiments were demobilised and disbanded; however, the brigade briefly existed as a part-time militia formation in New South Wales until 1921 when its regiments were reorganised into cavalry brigades.

The 94th Aero Squadron was a United States Army Air Service fighter squadron that fought on the Western Front during World War I. The squadron was assigned as a Day Pursuit (Fighter) Squadron as part of the 1st Pursuit Group, First United States Army. Its mission was to engage and clear enemy aircraft from the skies and provide escort to reconnaissance and bombardment squadrons over enemy territory. It also attacked enemy observation balloons and performed close air support and tactical bombing attacks of enemy forces along the front lines.

The Revolutionary Insurgent Army of Ukraine (Ukrainian: Революційна Повстанська Армія України, Revoliutsiina Povstanska Armiia Ukrainy; RIAU), also known as Makhnovtsi (Ukrainian: Махновці), named after their founder Nestor Makhno, was an anarchist army formed largely of Ukrainian peasants and workers during the Russian Civil War. They protected the operation of "free soviets" and libertarian communes by the Makhnovshchina, an attempt to form a stateless anarcho-communist society from 1918 to 1921 during the Ukrainian War of Independence.

The Persian Cossack Brigade, also known as the Iranian Cossack Brigade (Persian: بریگاد قزاق, Berīgād-e qazzāq), was a Cossack-style cavalry unit formed in 1879 in Persia (modern Iran). It was modelled after the Caucasian Cossack regiments of the Imperial Russian Army. Until 1920, it was commanded by Russian officers, while its rank and file were composed of ethnic Caucasians and later on Persians as well. During much of the brigade's history it was the most functional and effective military unit of the Qajar dynasty. Acting on occasion as kingmakers, this force played a pivotal role in modern Iranian history during the Persian Constitutional Revolution, the rise of Reza Shah, and the foundation of the Pahlavi dynasty.

The 46th Yekaterinoslav Rifle Division (Russian: 46-я Екатеринославская стрелковая дивизия) was an infantry division of the Red Army during the Russian Civil War.

The 13th (North Canterbury and Westland) Regiment was a territorial infantry regiment of the New Zealand Military Forces. It was formed in 1911 from various volunteer corps raised during the second half of the nineteenth century. Men from the regiment saw combat in the First World War as part of the Canterbury Infantry Regiment. It was amalgamated with the 12th (Nelson and Marlborough) Regiment to form the 2nd Battalion, Canterbury Regiment in 1921, which was redesignated as the 1st Battalion, Nelson, Marlborough and West Coast Regiment in 1923.

The 2nd (South Canterbury) Regiment was a territorial infantry regiment of the New Zealand Military Forces. It was formed in 1911 from various volunteer corps raised during the second half of the nineteenth century. Men from the regiment saw combat in the First World War as part of the Canterbury Infantry Regiment. It was amalgamated with the 1st (Canterbury) Regiment in 1921 to form the 1st Battalion, Canterbury Regiment.

6th Sich Rifle Infantry Division - an infantry division of the Ukrainian People's Army. It fought in the Kiev offensive of 1920 and in further actions against the Red Army, including the Battle of Komarów. The division operated as part of the Polish 2nd Army [pl] from April to May, and then as part of the Polish 3rd Army [pl] from May to August.

The Air Fleet of the Revolutionary Insurgent Army of Ukraine was one of the branches of the Revolutionary Insurgent Armed Forces.

The 1st Army was a field army of the Red Army during the Russian Civil War. The 1st Army was formed twice. The first formation was between the beginning of March 1918 and May as a reaction to the Austro-German occupation of Ukraine. The second formation was created on June 19, 1918, as a part of the Eastern Front and from August 15, 1919 as a part of the Turkestan Front. The Army was disbanded in January 1921.