AFAIK, radar modulators were usually just for switching PFNs, so didn't have to handle pulsed CW; an IGBT would do just as well (and indeed, does to this day, as pulsed klystrons are used in particle accelerator applications; I don't know anything about modern radar, but they probably still use pulsed magnetrons in the simpler (commercial) ones?).
If you needed to do pulsed CW at a few MHz (probably not much over 30MHz, given the size of the thing), you'd be able to get off more than a few cycles of something pretty mean, though.
It would be pretty expensive to do the same (or at much higher frequencies) with SS.
Tim