The Eastern District Defence Scheme (corrected to June 1904) assumed that Harwich would be the main enemy target, with the possibility of raids elsewhere along the coast with the purpose of doing damage or sabotage. Harwich was considered to be the most important fortress on the East Coast due to its closeness to Continental ports, which rendered it liable to naval attacks or an attack with the object of seizing Parkeston Quay as a disembarkation place for an invading army. A naval demonstration in support of landings elsewhere on the coast with a view to capturing the fortress from the rear was considered the most likely form of an enemy attack to have to be met.
Naval attack could either be by:
Heavy ships and cruiser raids which would have to bombard the port form a distance as the approach to Harwich was unsuitable for ships drawing more than 22 feet of water. Such an attack would be met by the heavy guns of the fortress (9.2” and 6” BL guns).
An attack by torpedo boats which would be met by Q.F. guns, minefields and infantry fire , assisted by eclectic lights at night.
Landings outside the defended area would almost certainly be made in conjunction with a naval attack and would either be focused on Harwich or Landguard.
An attack on Harwich would be made by landings in the vicinity of Walton-on-Naze or Clacton-on-Sea. Any force landed in these areas could be expected to reach Harwich within a few hours. The line selected to defend Harwich was the peninsula formed by the sea and the River Stour from Ray Island Hill, south-west of Pakeston on the north to the beach on the south. It was intended to occupy the key tactical points only, not the whole of the line. These were (from north to south):
Ray Island Hill
Fields adjoining the main roads leading to Harwich
The beach in the vicinity of the position-finding transmission cells.
To watch the peninsula south and east of a line from Manningtree to Wivenhoe, a strong cyclist picket was suggested, to be based about Weeley with strong pickets at Walton-on the Naze, Clacton-on-Sea and Brightlingsea.
When the Harwich Fortress Defence Scheme was drawn up it was expected that Landguard would be a more likely target than Harwich as it was further away from any mobilization centres of any mobile column of the Field Army. As Landguard would have to hold out longer before any relief could arrive, stronger defences than Hariwch were planned.
The line chosen for the defence of Felixstowe was the high ground, Railway Hill, to the north of Landguard Common, which extended across the peninsula formed by the sea and the northern outskirts of Felixstowe on the east to the Martello Tower “N” at Walton on the west. It was deemed vital to hold this high ground as if occupied by the enemy they would be able to make use of it to bombard the Landguard batteries, submarine mining buildings etc. It was also a good defensive position as the lines of communication would be concealed all along the line. It did however require that the whole of Felixstowe town would have to be held to secure the position’s right flank. The planned position, as at June 1904, then generally followed the line Goyfield House-Langley Farm-“N” Tower, Walton battery, with Walton village to be fortified and held as an outpost to the line. This was more or less the line prepared during 1914-16 but the line ran to the north of Walton village, generally from Goyfield House-Vicarage-Ferry House Inn-“N” Tower, Walton battery. A series of positions were also constructed to defend the beaches to the north of Felixstowe, and the approaches to the town from the north.
A strong cyclist picket was to be posted at Wickham Market, with posts all along the coast south from Southwold, particularly at Bawdsey and Felixstowe.
Work began on preparing the Harwich and Felixstowe positions in 1914 and a scheme to strengthen the defences was carried out in 1916. The defences consisted of closed groups of trenches sited to cover the vital approaches. The trench positions were surrounded by a wire obstacle, in places up to three rows of wire deep, and a continuous wire obstacle linked up the positions that formed the Felixstowe defences. The positions consisted of fire trenches linked by communication trenches, some with overhead cover. Trench shelters were provided. Buildings inside the positions were fortified for defence and walls loopholed. Field works were constructed for machine guns and lights. Hedgerows were removed were necessary to improve fields of fire. The works were constructed with both military and civil labour. On the seafront concrete parapets were constructed in places for riflemen. Mines, which would be fired electrically, were laid.
Right: Concrete parapet, Felixstowe
Blockhouses were also constructed; these were typically 15 ft x15 ft or 12 ft x 12 ft square bullet proof constructions for eight rifles and a light machine gun or four rifles. The blockhouses were constructed by Special Service Section, 1st East Anglia Service Company. Later during further invasion scares, concrete pillboxes were added.