You are skilled at drawing in close to an opponent and making better use of a shorter weapon. As your Action, you can perform an Opposed Melee Test to attempt to step inside your opponent’s weapon length. The winner chooses if combat continues as normal or as ‘in-fighting’. During in-fighting, any weapon longer than Short counts as an Improvised Weapon. At the start of their Turn, an opponent may choose to lose Momentum in order to end in-fighting.

Core Book, Page 121