Sunderland was classified as a C Class Commercial Port in 1905 and it was thought that one battery of two 6-inch BL guns would be sufficient defence.
However, the geography did not allow a single battery to cover the whole harbour, so it was recommended that there be two batteries, one to the North and the other to the South in the Hendon area.
The Northern Battery was Rocker Battery, although all the RML guns had been removed by 1902.
Abb’s Battery was later built a few hundred yards to the south of Rocker Battery.
Wave Basin Battery was built in 1860 inside the actual harbour area.