Steynewood Battery had the shortest active service of any battery or fortification on the Isle of Wight, and was only armed and in service for two years between 1896-1898. Steynewood Battery was a victim of the unprecedented rate of change in military technology at the end of the 19th Century, when military technology became outdated faster than it was possible to build batteries and fortifications capable of housing it or defending from it. In less than a hundred years, the epitome of military design changed from a wooden sailing ship in the 1830s to the Spitfire in the 1930s.

The Original Plan

Steynewood Battery¹ was to be a new type of battery on the Island – a High Angle Battery, working on the same plunging fire principal as Puckpool Battery but with more modern and effective weapons than mortars. Built further inland than any other coastal battery on the Island in the Steyne Wood, the battery's purpose was to command the anchorage of St Helen's Roads and the approaches to the Nab Passage, preventing ships there bombarding Portsmouth Dockyard while out of the range of the other existing batteries.

The high angle guns were positioned inland so that they were hidden from an enemy fleet, who would not be able to counter-attack them.

The Theory Behind The Battery

Since the earlier forts built in the 1850s and 60s, British fortification theory had evolved. In the Russo-Turkish War of 1877-78² the Turkish army in the port of Plevna in Bulgaria resisted a vastly superior Russian army for five months. The Turks had made good use of magazine rifles and trenches.

In 1882 Sir Andrew Clarke became Inspector-General of Fortifications and Director of Works, and he wrote in 1886:

'For the future we must rely as much upon concealment as upon resistance... The power of small arms, which has grown concurrently with the improvements in ordnance, and the introduction of machine and quick-firing guns, have also had an important influence on the designs of works of defence... Defences if skilfully designed will be instinguishable from the ground on which they stand, and while they retain all the advantages of the defence, will offer no mark to the enemy's fire.'

The first forts built on this model were two infantry redoubts, Grange and Woodland, built to defend Chatham from attacks to the east. These two redoubts were known collectively as Fort Twydall as they were located near Twydall, Gillingham, in Kent. The Twydall profile, as it became known, emphasised the use of a glacis, iron palisades, infantry parapets and earthworks that were difficult to detect and target. In many ways these forms of forts predicted the trench warfare that was to dominate the Great War, with the iron palisades replaced with barbed wire.

Steynewood Battery

Steynewood Battery was constructed with three gun groups, each of two guns. As well as the main guns, defensive rifle trenches were emphasised, where infantry would be able to advance in front of the guns to defend from enemy attack. The defence was also aided by a steel palisade in the front, and rifle trenches also protected the rear of the battery. The battery's munitions were stored in intricate underground and bombproof cartridge and shell stores between the guns. The battery also had a guard room, cell, caretaker's quarters capable for use as prisoner's quarters, a well and accommodation for eight with the main garrison to be housed in Bembridge Fort.

Work began on building the battery in August 1889, the guns were delivered in 1893, and work finished in May 1894. However, the guns were not mounted until 1896, when only four of the proposed six 9-inch 12 ton guns were installed on their High Angle mountings. The final two were mounted in 1898, when there was a proposal to extend the fort to add two more; however, in 1899 the battery was instead disarmed.

The Drawback

Although defensively Steynewood Battery anticipated what would be Europe's largest and bloodiest defences – the trenches of the Great War – offensively it was considered a failure. The High Angle weapons were inaccurate due to the nature of the plunging trajectory of the projectile. The High Angle guns could fire between 30° to 70° elevation, and trials showed that between 42° and 64°, the time taken for a shell to reach its target was between 42 and 64 seconds. This would allow any enemy vessel plenty of time to manoeuvre out of harm's way. It was concluded that Steynewood Battery 'would not deter ships which would dare to face the powerful interior batteries. These guns are very slow in their fire and not very accurate'.

The battery was sold off in May 1909 for £700. As the original cost of purchasing the site was £1,500 with undisclosed sums spent on developing the site and building the battery, understandably questions were raised in Parliament in July 1909 about the sale. The official report states:

'Arthur Fell³ inquired of the Secretary of State for War if he sold in the month of May last the disused fort at Bembridge, in the Isle of Wight, known as Steynewood Battery, with 12 acres of freehold land adjoining; if the land cost the War Office £1,300; if it was sold for £700; and if the suitability of the site for a garage for dirigibles and aeroplanes, and for any other possible uses, had been taken into account before the sale was made?'

No satisfactory answers were given other than the site was unsuitable for any other possible military use. This, however, did not prevent its new owner, Sir John Thorneycroft, using the site as a test facility for Thornycroft Research and Development⁴. Sir John Thorneycroft designed and tested a mortar and depth charge thrower here in 1914. He also built a naval test tank in the grounds, which still exists. Many naval models were tested in the tank.

Steynewood Battery is still in the possession of the Thornycroft family as a private residence.