In the Deep Space 9 episode The House of Quark, Grilka says this about a political adversary:
There is no honour in what he has done. If he wanted to challenge my House, he should've made a declaration, met our forces in battle.
What forces is she talking about? Do Klingon Houses maintain their own armies?
According to the Star Trek: Klingon Bird-of-Prey Haynes Manual co-authored by Rick Sternbach (one of the two principal production designers for the TNG-era television series and several of the Star Trek films),
"Klingon society operates on feudal lines, with individuals and families pledging their allegiance to Houses, the greatest of which come together to form the High Council, which is led by the High Chancellor."
From this, we gather that warriors and families unrelated by blood to a particular House will pledge allegiance to that House and fight for it. So the "forces" referred to by Grilka would be warriors and families that have sworn an oath to her House.
