Historians are divided about the people who were part of the fyrd. These men would have been a mix of the "fyrd" and housecarls. It appears that the hundred was the main organising unit for the "fyrd". However, the major innovation is in the organization of the Fyrd. The housecarls were replaced with members of the "fyrd", and the shield wall held. The estate also served as a home for Grith Fyrd during the 1930s. Glaister had been involved in the Grith Fyrd barter for work system. The "fyrd" usually served for two months, except in emergencies. Large regions could be devastated before the fyrd could assemble and arrive. He also updated the traditional fyrd to provide a standing army and navy. It was the responsibility of the shire fyrd to deal with local raids. In Anglo-Saxon times, defences were based on the "fyrd".