I just tried Battle Isle 2 and after getting frustrated with capturing the town on the second level I looked through the manual for clues and, failing to find any, turned to Google. From my search, I found out that only infantry and the basic reconnaissance vehicles (Rangers, not the Buggies that can shoot two hexes away) can capture vehicles.

I see that this detail was mentioned in the manual for the original Battle Isle and I suspect the writers of the manual for Battle Isle 2 would expect users to know this already without having to be told. However, I, starting to play a Battle Isle game for the first time ever in early 2019, didn't like the interface of the original game and skipped to Battle Isle 2 immediately without reading the Battle Isle 1 manual more thoroughly. I am leaving this here to help other new users of the series.