M-55S in the 2014 Russia-Ukraine War

Direct proof of use

Slovenia publicly announced on September 19, 2022 that Ukraine would receive 28 Slovenian M-55S tanks through a ring exchange with Germany. Ukrinform later reported that Ukraine had received the same 28 tanks and that Slovenia's Ministry of Defense confirmed the delivery.

Later evidence places the tanks in Ukrainian service rather than only in transfer paperwork. Tank Encyclopedia traces the first confirmed Ukrainian sighting to December 9, 2022 and describes subsequent use by Ukrainian units, including indirect fire by the 127th Territorial Defense Brigade in March 2024. Defense Express reported in March 2026 that crews of the 159th Separate Mechanized Brigade were operating M-55S tanks during training, while Oryx separately listed visually documented Ukrainian M-55S losses.

Sources: Slovenian Government Ring Exchange Announcement, Ukrinform Ukraine Receives M-55S, Tank Encyclopedia Ukrainian Service, Defense Express Continued Operation, Oryx Ukrainian Equipment Losses

Timeline

The documented sequence begins with Slovenia's September 2022 transfer decision, followed by receipt reporting in late October 2022 and the first confirmed Ukrainian-service sighting in December 2022.

Open-source reporting then shows the small fleet moving through several Ukrainian service contexts: training and reassignment after arrival, front-area damage and losses around Kreminna in 2023, indirect fire activity with the 127th Territorial Defense Brigade in March 2024, and continued training or operation with the 159th Separate Mechanized Brigade in 2026.

Sources: Slovenian Government Ring Exchange Announcement, Ukrinform Ukraine Receives M-55S, Tank Encyclopedia Ukrainian Service, Defense Express Continued Operation

Narrative

The M-55S entered the war as a Western-supported emergency armor transfer rather than a modern tank procurement. Slovenia had modernized the T-55 into the M-55S standard in the 1990s, including a 105 mm L7-type gun and NATO-compatible ammunition, but the Ukraine transfer involved a small stored fleet of 28 vehicles.

In Ukrainian service, the M-55S appears to have been used cautiously. Tank Encyclopedia reports that the 47th Separate Mechanized Brigade first fielded the type mainly for training before the vehicles were reassigned, and later identifies use near Kreminna, where several tanks were hit or destroyed in July 2023. The same account describes the 127th Territorial Defense Brigade using M-55S tanks for indirect fire with drone-assisted correction in March 2024.

By 2026, reporting still placed surviving M-55S tanks in Ukrainian hands. Defense Express cited brigade-released photos and videos of 159th Separate Mechanized Brigade crews operating the tanks during training and noted additional field protection fitted to the vehicles. Oryx's visually documented loss list records multiple Ukrainian M-55S losses, supporting that the transferred fleet was exposed to wartime attrition after delivery.

Sources: Slovenian Government Ring Exchange Announcement, Tank Encyclopedia Ukrainian Service, Defense Express Continued Operation, Oryx Ukrainian Equipment Losses