The Mersey Estuary was designated as a Class C commercial port by the Home Ports Defence Committee in 1905. Defences in the area included:
Fort Perch Rock was built in 1830 and armed with 18 smooth bore guns.
In 1861 it was upgraded to mounted two 7-inch RBLs, eight 68-pdr SB with eight 32-pdr SB retained.
In 1875 the eight 64-pdrs replaced the 68-pdrs.
1897 three 6-inch Mark VI guns.
1909 the three 6-inch BL guns upgraded to Mark VIIs.
Magazine or Liscard Battery was built in 1858 was armed with seven 10-inch smooth bore guns.
The battery was never upgraded and was declared obsolete by 1912.
Seaforth Battery was constructed between 1877 and 1879 to mount four 12.5-inch RML guns
In 1898 two 4.7-inch Q.F. guns were installed on the roof of the casemates
In 1905 the four 12.5-inch RML guns were withdrawn
This site has been lost to development
Fort Crosby was a new battery in 1905, mounting three 6-inch BL Mark VII guns
It is believed the guns were mounted in 1907
The Battery site was used for Anti Aircraft Guns in World War 2