The Rocket Launcher T34 (Calliope) was a special modification of the second variant of the early-generation Medium Tank M4 (Sherman) family. The U.S. Ordnance Department initiated a series of projects experimenting with the attachment of rocket launchers to the M4 Sherman, in order to provide enhanced firepower to its infantry. Despite the fact that its 75 mm M3 tank gun was capable of firing very efficient ammunition, it was unable to handle massive waves of assaulting enemies. Furthermore, it was also insufficient against the Germans' heavily entrenched strongholds. Although not as precise as traditional artillery, rockets can cover a bigger area in less time with explosives and shrapnel, saturating a target in seconds. Rockets also have a negative psychological impact on enemies under rocket attack because of the howling sounds they make as they fly through the air. The most renowned of these tank-mounted rocket launchers was the Rocket Launcher T34, which was called "Calliope" after a type of steam organ due to the deafening roar that burst from the tubes when the rockets were fired, as well as the launcher's appearance

Introduced in Update 1.49 "Weapons of Victory", the Calliope is a unique modified M4 Sherman capable of firing rockets (60 rockets in total) at adversaries as a secondary weapon. Originally designed for anti-infantry use, the 114 mm M8 rockets with high-explosive (HE) warhead rockets carry high explosive warheads that can effectively destroy light enemy vehicles and damage heavier armoured targets sufficiently to make the enemy's repair time extremely long and miserable. It is advised to use many rockets on enemies since a single rocket is frequently insufficient to damage them. Furthermore, the weapon, like any other ground vehicle firing unguided rockets, would emit an extremely loud but distinct firing signature, allowing opponents to identify the type of vehicle as well as its location on the map. The unique smoke trail left by fired rockets might potentially reveal the player's location. However, the M8 rockets' faster fire rate enables many volleys of rockets to be fired at a target in rapid succession. The resulting flash, fire, and smoke effects of continuous bombardment on a target can temporarily blind targets and can thus be employed as an emergency smoke cover. However, the rocket should not be used as a primary anti-tank weapon because it lacks the explosive strength and penetration to successfully destroy tanks. The Calliope's primary weapon is the 75 mm M3 tank cannon, which is more than capable of engaging most opponents in its ranks.