My image of the two great wars of the early 20th century is pretty much an infantry/artillery/tank picture. Does cavalry belong too?
^ These answers I've given should be pertinent!
Does cavalry belong too?
It most certainly does! In WWI it was the only arm capable utilizing mobility, shock and firepower to the greatest effect on the battlefield. It really wasn't until the mid-1930s that tanks could be said to replace them, and even still cavalry served with distinction in WWII.
Some examples, I have more in the answers I've listed, include the Italian Cavalry Corps at Vittorio Veneto, the British Cavalry Corps at Amiens and Le Cateau, the French 1st and 2nd Cavalry Corps along the Lys and Ourcq Rivers, the (former) Indian Cavalry Division in Mesopotamia, the French Cavalry Brigade at Uskub, and the Desert Mounted Corps in Palestine. All of these examples are from 1918, and in the Italian, French and Middle Eastern cases played crucial roles in the final Allied victories. In WWII, Soviet Cavalry Mechanized Corps contributed to the advances of 1944-45, while Lev Dovator's Cavalry Corps tied down considerable enemy forces behind German lines in the winter of 1941-42. The Italian 33rd Cavalry Division routed an infantry regiment at Izhbushenskii, along the Don River in 1942, and the Polish Cavalry Brigades contributed to the defence of Poland in 1939, notably at Krojanty. Janusz Piekalkiewicz's book The Cavalry of World War II is a solid read if you can find it, as is David Dorondo's Riders of the Apocalypse, about German cavalry from 1870 to 1945.
Here are some sources for anyone interested. Firstly, [Stephen Badsey’s] (https://www.repository.cam.ac.uk/bitstream/handle/1810/244878/Badsey12201.pdf?sequence=1&isAllowed=y) and [David Kenyon’s] (https://dspace.lib.cranfield.ac.uk/bitstream/1826/3032/1/D%20Kenyon%20Thesis%20corrected.pdf) theses on the British cavalry before and during WWI. Then the [US Cavalry (later Cavalry-Armour) Journal] (http://www.benning.army.mil/library/content/Virtual/CavalryArmorJournal/) (note however that the link might not work at times), and the [Combined Arms Research Library Digital Library] (http://cgsc.contentdm.oclc.org/cdm/search/searchterm/cavalry/mode/all/page/3), of Fort Leavenworth. For anyone that can read French, there are a couple issues of the French Revue de Cavalerie available online [here] (http://gallica.bnf.fr/ark:/12148/cb328569976/date), and a Colonel Poudret published a number of essays on cavalry in the Great War in the Revue Militaire Suisse during the 1920s, available online [here] (http://www.e-periodica.ch/digbib/volumes?UID=rms-001). As for books, Wilhelm Balck’s (Hermann Balck’s dad) book “Development of Modern Tactics - World War” is available [here] (https://archive.org/details/developmentoftac00balc), as is Richard Preston’s [“The Desert Mounted Corps,”] (https://archive.org/details/desertmountedcor00pres), Malcolm Wheeler-Nicholson’s 1922 book [“Modern Cavalry,”] (https://archive.org/details/moderncavalrystu00wheerich) and even Douglas Haig’s 1907 [“Cavalry Studies.”] (https://archive.org/details/cavalrystudiess00haiggoog) The University of Toronto also has four volumes of the British cavalry journal online, for [1922,] (http://contentdm.ucalgary.ca/cdm/compoundobject/collection/cmh/id/61393/rec/37) [1925,] (http://contentdm.ucalgary.ca/cdm/compoundobject/collection/cmh/id/52103/rec/38) [1926] (http://contentdm.ucalgary.ca/cdm/compoundobject/collection/cmh/id/55008/rec/39) and [1927.] ( http://contentdm.ucalgary.ca/cdm/compoundobject/collection/cmh/id/64705/rec/40)