The first video has appeared online depicting the Ukrainian army’s ex-Slovenian M-55S tanks. The video depicts what appears to be a four-person M-55S crew training on its new-old vehicle. The thick mud—a sticky hallmark of Ukraine’s wet early winter—might confirm the video is recent. The M-55S despite its age could represent a glimpse at the Ukrainian army’s tank future. It’s all about the gun. The M-55S is a deeply modernized Soviet T-55, a tank type that first entered service in the late 1950s. In the 1990s, the Slovenian army paid Israeli firm Elbit and STO RAVNE in Slovenia to modify...