The Ukrainian tank crew members told CNN that what they really need is artillery and aviation assets. “We have no aviation and artillery. We have only tank. And it’s the problem,” one soldier said.

The soldiers also complained that the Abrams tanks are not well suited for the environment, specifically the rain and fog, which they say has damaged the electronic equipment inside the tanks.

“Some of the indicators they talked about like condensation on the instruments — that’s BS,” Hertling told CNN’s Jessica Dean. He argued that the Abrams tank was built for war in Europe. This tank was built with the Soviet threat in mind.

The former tanker and commander of United States Army Europe dismissed the Ukrainian soldiers’ claims that the tank has the wrong kind of ammunition and that it couldn’t bring down a house even after 17 rounds were fired into it.

The general said that “I know for a fact having fired these vehicles and having been a tanker all my life that this is a crew that is not either selecting the right weapon system or isn’t maintaining their tanks very well.”

Hertling said he spent three decades on the Abrams in Europe and didn’t encounter the problems that the soldiers described. He suggested they were simply complaining because the vehicle broke down, noting that disgruntled tankers will sometimes give every reason for why something is not working or why “this piece of crap” is something they don’t need.

That said, the Abrams “was not the best tank to give to Ukraine because there are maintenance challenges and you have to have a highly trained crew,” he said. But “Ukraine continued to ask for these vehicles even though they knew there was a high maintenance standard to keep them running.”

Throughout the war, Ukrainian troops have had to learn how to use a wide variety of systems, some more complicated than others. The Abrams, particularly the engine, is a complex system. And maintenance has long been a concern.

A Department of Defense Office of Inspector General report from February concluded that there wasn’t a plan for sustainment and that “without deliberate and planned sustainment support, including proper spare parts, ammunition, and maintenance support, the Ukrainians would not be capable of maintaining these weapon systems in their ongoing fight against Russia’s full-scale invasion.”

All 31 of the Abrams tanks the US provided are currently in service with the 47th Mechanized Brigade.