Because Nazi Germany was inclined to do battle by attempting sweeping encirclements, starving and forcing surrender of enemy units, they ended up capturing a lot of weaponry from their enemies. Due to Nazi Germany’s disadvantageous resource situation compared to its opponents, much of this equipment was pressed into service for some use or another.
Equipment that was obsolete was handed to second-line and security units in occupied territories. Tanks however were often rolled into Panzer divisions or Panzergrenadier divisions, under the moniker of “Beutepanzer” which literally means “prize tank” but is also sometimes rendered as “trophy tank” in various wargaming materials of dubious quality.
One of the first major uses of Beutepanzer was after the fall of France. France had a lot of decent tanks for the time, and a good few were used to fill in the “scouting roles” of utter benchwarming shit like the Panzer II. During Barbarossa the Wehrmacht captured a lot of Soviet equipment and also deployed it, including Beutepanzers. Many times, equipment was captured intact, often because of poor operational leadership on the Soviet side leading to mass surrenders or the abandonment of heavy weapons without any attempt to sabotage them first.
Here for example we have a T-34 with a bunch of Germans on it.
In theory, getting a Beutepanzer was like getting a tank for free. Germany didn’t have to waste precious resources to make it, and a lot of the times they had enough ammo to keep it shooting for a while. Particularly with Soviet tanks, the Beutepanzer could fulfill the role of a line tank like the Panzer IV perfectly and slot in tactically without problems. Even Elite units like the Das Reich used Beutepanzers! The Das Reich boasted a whole unit of captured T-34s in Kursk.
In practice, Beutepanzers led to a massive clusterfuck of logistics in an army that already suffered from having an arsenal clogged with tons upon tons of fucking vehicles and vehicle modifications. Cronyism at every level of development led to companies each building their own stupid vehicles and versions of existing vehicles with their little idiosyncratic touches to them that all needed their own spare parts and servicing and technical know-how to deal with. On top of that system you had the Beutepanzers. Now suddenly logistics personnel and engineering staff also had to deal with tanks from whole other countries that they didn’t readily have access to parts for, didn’t have a renewable supply of ammo for, etc. You could have 9-10 different model tanks in one unit, with half of those being from outside Germany!
Sometimes they solved that problem by just giving that shit away. Romania got a ton of Soviet shit. It didn’t really do much to make Romanian units anything more than a gradual trainwreck.
That’s a KV-1 given to Finland. For whatever reason Finland rolled with a huge Swastika on that shit rather than an iron cross like normal Axis.
The Germans were not the only ones who captured tons of enemy equipment. In Demyansk but to a much, much greater scale in Stalingrad, enemy equipment was acquired by the Soviet Union. But Soviet logistics relied on simple equipment that was easy to repair or replace and that was mass produced in the motherland and traveled on a relatively short and steady supply line to the front, and German equipment was very much not that, and fit poorly in Soviet units.
The MG42 for example was a much more complicated device than the Soviet Degtyarov and Maxim machine guns, with many more parts, many small parts, and more labor-intensive to manufacture. Handing an MG42 to a unit was not so simple. Similarly German tanks were difficult to field repair for anything more complicated than a busted track, and had complicated systems like electrical turrets and gyro stabilized guns that could not be easily replaced or repaired in the Soviet Union.
A lot of the times captured German shit was dismantled and studied by the Soviets or shot at for ballistic studies, instead of used outright.
Other Allies did a lot less capturing, mostly because they did a lot less fighting of enemies with decent shit to capture in general. Japanese equipment was not great compared to American and British equipment, and the Americans and British were not fighting the Germans in circumstances where they could potentially capture a ton of stuff. However, they did manage to get some pieces, such as a Tiger tank in Tunisia. But they mostly studied the equipment, rather than use it.