旗本 はたもと はち まん であれば
hatamoto hachimankideareba

Noun
Da Copula

The "-eba" conditional form ("if/when…") of 旗本八万騎

1. If/When the 80,000 banners/flags of the retainers…; If/When having 80,000 banners/flags of retainers…

Ba Conditional