The 298 LT vz. 35 tanks were assigned to the armored regiments belonging to the four Mobile (Rychlá) Divisions between 1936—39. Each regiment was supposed to detach three-tank platoons to support the infantry divisions and border areas in times of crisis. These platoons were heavily used suppressing the protests and violence instigated by Konrad Henlein's Sudeten German Party (Sudetendeutsche Partei - SdP) and the Sudetendeutsche Freikorps (paramilitary groups trained in Germany by SS-instructors) between May and October 1938.
After the Munich Agreement two tank battalions were sent to reinforce the 3rd Mobile Division in Slovakia. They were used to repel Hungarian and Polish border-crossers, sometimes up to a battalion in strength. They screened the infantry when they had to evacuate southern Slovakia after the First Vienna Award on 2 November 1938.
A company of nine LT vz. 35s was in Michalovce when Carpatho-Ukraine declared independence and Hungary invaded on 14 March 1939. They bolstered the Czech defenses in front of Svaliava before being forced to retreat into Slovakia by 17 March. They were turned over to Slovakia the next day. The S-II-a prototype and one LT vz. 35 tank were returning from testing in the Soviet Union when the fighting began. They detrained in Sevljus and participated in a counterattack at Fancíkovo, but the LT vz. 35 was damaged and captured by the Hungarians. The prototype was forced to retreat into Romania by 17 March, along with most of the other Czech troops in eastern Ruthenia. The Romanians returned it to Škoda six months later.
In 1939, following the German occupation of Czechoslovakia in March 1939, 244 vehicles of the Czechoslovak Army were seized by the Germans where they were known as the L.T.M.35 until January 1940. In German service, they were used as substitutes for the Panzerkampfwagen III medium tank. They were assigned to the Panzer Battalion (Panzerabteilung) 65 (39) of the 1st Light (leichte) Division and the independent Panzer-Regiment 11 (81) where they participated in the Invasion of Poland. 77 of these were lost during the campaign, mostly due to mechanical breakdowns, but only 7 of these were irreparable. From 1940 on there had not been any spare parts available and tanks had to be completely rebuilt to remain operational.
The 1st Light Division absorbed the 11th Panzer-Regiment and was redesignated as the 6th Panzer Division on 18 October 1939 It took 132 Pz.Kpfw. 35(t)s into the Battle of France where it was assigned to XXXXI Corps (mot.) for Panzergruppe von Kleist's attack through the Ardennes 44 of these had been lost by the end of May. 35 replacements were issued on 3 June in preparation for Fall Rot, the attack on the remnants of the French Army that began the following day. A total of 62 Pz.Kpfw. 35(t)s were either total write-offs or were damaged beyond the ability of the field maintenance workshops to repair during the campaign.
For the invasion of the Soviet Union 6th Panzer Division had 160 Pz.Kpfw. 35(t)s. to support 4th Panzer Group's drive on Leningrad. By 10 September 1941 the division had only 102 operational Pz.Kpfw. 35(t), despite having received 2 replacements from Germany. 8 tanks were repairable, but 47 were total losses. By 31 October only 34 were operational with another 41 requiring repair. On 30 November all Pz.Kpfw. 35(t)s were reported non-operational.
The average distance driven is 12,500 kilometres (7,800 mi) for the Pz.Kpfw. 35(t). The special situation in regard to repair the Pz.Kpfw. 35(t) is well known. It is indeed deemed necessary to point out that repairs can only be accomplished by cannibalizing other Panzers because there are no longer any spare parts for the Pz.Kpfw. 35(t). This means that after retrieval of the Panzers that are scattered around the terrain, a maximum of 10 can actually be repaired out of the 41 Pz.Kpfw. 35(t) reported as needing repair. The Pz.Kpfw. 35(t) can no longer be rebuilt. All of the components are worn out. To be practical, maybe the armored hulls are still useable.
Due to the cessation of production of these tanks and the absence of spare parts being made, it was decided the summer campaign of 1941 was to be their last. The fighting in Russia exposed the vehicle's unsuitability for cold weather operations and general unreliability. This weakness, in addition to their thin armor and inadequate firepower, resulted in the 6th Panzer Division being reequipped with German tanks upon its withdrawal from Russia in April 1942. All 26 remaining Panzer 35(t)s still in working condition in 1942 were sold to Romania. Some vehicles had their turrets and hull machine guns removed so that the chassis could serve as a munition carrier or an artillery tractor, the Artillerie Schlepper and the Mörserzugmittel 35(t). These had a towing capacity of 12 tonnes (12 long tons; 13 short tons).
Romania ordered 126 of the tanks on 14 August 1936 as the R-2 and received the first 15 in April–May 1937 to display in a parade although they had to be diverted from the Czech order. They suffered from numerous teething problems and the Romanians put a hold on production until these issues were resolved. The constantly changing Romanian demands didn't help the situation, but they refused to accept any vehicles until trials were conducted in Romania. Three R-2s were shipped to Romania on 12 July 1938 for the trials, but Skoda knew which one would be chosen and prepared the vehicle well and it passed all tests. After disassembly and checks of the trial tank was completed the Romanian commission approved the design on 23 August. In the meantime the initial batch was returned to Skoda to be upgraded to current standards on 28 July. Shipments to Romania began on 1 September with 27 shipped before the Munich Crisis forced the Czechs to hold all remaining tanks in case they were needed. 5 finished tanks and 6 almost-finished tanks were appropriated and shipped to Slovakia although they were quickly returned after the Munich Agreement was signed. The last shipment departed on 22 February 1939.
The R-2s were assigned to the 1st Armored Regiment of the 1st Armored Division where they participated in Operation Barbarossa. The division was withdrawn from combat after the Battle of Odessa in 1941. It returned to the front on 29 August 1942 with 109 R-2s. By the eve of the Soviet Stalingrad Counter-offensive on 19 November the division could only muster 84 serviceable R-2s with as many as 37 unserviceable tanks stationed in the rear. The division was on the outer edges of the Stalingrad Pocket, but managed to breakthrough the western wing of the encirclement, although 77 R-2s were lost in the process. Only about a third of these were destroyed by the Soviets, the rest were either abandoned or broke down and couldn't be recovered. One R-2 arrived from Romania during December as a reinforcement. The 1st Armored Division was ordered home in early January 1943.
Despite the delivery of 26 Pz.Kpfw. 35(t)s during 1942, Romania could only muster 59 R-2/Pz.Kpfw. 35(t)s on 1 April and 30 August 1943, but raised this to 63 by 25 March 1944. There were 44 on hand on 19 July 1944. By this time they were relegated to training duties with the 1st Training Armored Division. A company of R-2s was sent to Transnistria with the ad-hoc Cantemir Mixed Tank Group on 24 February 1944, but it did not see combat before being withdrawn on 28 March 1944.
A company of R-2s was assigned to the Popescu Armored Detachment after King Michael's Coup and Romanian's defection from the Axis at the end of August 1944. The Detachment was tasked with preventing the German units stationed around Ploie?ti from breaking out to the north and finding refuge in Hungary. They accomplished their task and the R-2s were withdrawn from combat operations until the following year. Romania had concentrated all of its remaining tanks and armored fighting vehicles in the 2nd Armored Regiment in early 1945 as the unofficial Soviet arms embargo began to have effect. It had five R-2s on hand in early February 1945 when it was sent to the front, but the Soviets confiscated most of them when it arrived. Both R-2s were serviceable when the regiment entered Bratislava on 4 April 1945, but these were probably destroyed when the regiment was virtually surrounded in Austria on 10 April because they are no longer listed among the regiment's vehicles afterwards.
Twenty-one tanks were rebuilt as TACAM R-2 tank destroyers with an ex-Soviet 76.2 mm gun in 1943—44.
The Slovak Army seized a total of 52 LT vz. 35 tanks when they declared their independence from Czechoslovakia in March 1939. They were organized into a battalion that was later incorporated into the Armored Regiment. Three of these tanks participated in the Slovak-Hungarian War of March 1939. One tank company participated in the invasion of Poland, but didn't see any fighting. The Army upgraded the internal communications system of its tanks with German intercoms in 1941, but it unknown if they added a fourth crewman as did the Germans. When Slovakia joined the German invasion of the Soviet Union it sent a Mobile Group that included thirty LT vz. 35. The Mobile Group was reinforced and reorganized in early July 1941 as the Mobile Brigade, also known as Brigade Pilfousek after its commander, and it mustered only 27 tanks despite 7 reinforcements because breakdowns had caused 10 tanks to be evacuated back to Slovakia. This was due to a conspiracy among the Slovak tankers that the tanks would be needed to overthrow the regime at some point and couldn't be wasted in combat against the Soviets. This caused a high incidence of crew sabotage to which the officers and maintainers turned a blind eye, which caused the tanks to be withdrawn to Slovakia at the beginning of August 1941. On 1 January 1942 the Slovaks had a total of 49 LT vz. 35 on hand because three had been destroyed in the battle for Lipovec earlier in the summer. However, of these 49 only 7 were operational as part of the conspiracy to keep the tanks in Slovakia The LT vz. 35s were relegated to the training/reserve role by 1943 when the Germans began to supply more modern tanks to Slovakia. At least eight LT vz. 35s were used by the insurgents during the Slovak National Uprising in 1944.
Bulgaria used 26 tanks, delivered by Germany in early 1940, with the normal A-3 gun and 10 T-11 tanks with the more powerful A-7 gun from the confiscated Afghan order were delivered between August and October 1940. They were supposedly relegated to training duties once the Germans began to deliver Panzerkampfwagen IV medium tanks in 1944, but apparently remained in service into the Fifties. But Kliment and Francev claim that the T-11s participated in the fighting in Yugoslavia and ended the war south of Vienna as part of the 1st Tank Brigade.
Hungary captured one LT vz. 35 in Carpatho-Ukraine on 15 March 1939, when it conquered that country, and another in fighting with the Slovaks on 24 March 1939. They were impressed and asked Škoda for a quote to repair them. The Hungarians did not accept the price but Škoda fixed them for free once the Hungarians had bought a license to build the medium 40M Turán I tank in August 1940. The tanks were returned to Hungary in March 1941 and were used for training through 1943.