I've made it to level 100 several times, yet can't defeat it. One thing…

I've made it to level 100 several times, yet can't defeat it. One thing I have found to be very helpful is as you finish a board, try to have the bonus full so you can carry it to the next board. Don't use it if you don't need it and keep adding bonuses for the more difficult boards. Does anyone know how you actually get extra men?