LogFAQs > #962305047

I've never done an endgame route with the Minutemen in Fallout 4, but from what I've read it sounds like it applies to this topic: the third-to-last quest involves defending the Castle against waves of Institute forces, and then the final quest (assuming you've made enemies with the Brotherhood of Steel) involves defending the Castle again from Vertibirds after your artillery strikes destroy the Prydwen.

And while the Institute endgame route doesn't fit this bill due to the player deliberately infiltrating the Boston Airport for the purpose of reprogramming Liberty Prime to shoot down the Prydwen, it does have a slight 'hold your ground' feel in that waves of generic BoS troops - as well as all the named BoS members - will sequentially swoop in on the airport and try to stop you, with Elder Maxson being the final arrival.