1:35 scale is the most popular scale for model military vehicles, with an extensive lineup of models and aftermarket parts available from a wide variety of manufacturers.
The roots of 1:35 as a military modelling scale lie in early motorized plastic tank kits. To accommodate electric motors and gearboxes, these models needed to be made in a larger scale. There were many companies making such tanks, but it was Tamiya’s example that made 1:35 a de facto standard.
According to Shunsaku Tamiya in his book Master Modeler (page 63):
“After the success of the Panther, I thought it would be a good idea for us to produce other tanks from different countries in the same scale. I measured the Panther and it turned out to be about 1/35 of the size of the original. This size had been chosen simply because it would accommodate a couple of B-type batteries. Tamiya’s 1/35 series tanks eventually got to be known around the world, but this is the slightly haphazard origin of their rather awkward scale”.