Heligoland fortifications and a ruddy great bang.

A bit more research turned up some interesting data and photos of Heligoland Island's fortifications circa 1918. The main armament appears to have consisted of two battleship-type gun turrets mounting two 12"/30.5cm guns apiece, along with a number of smaller turrets mounting 8.25"/21cm guns.

30.5cm turrets. Note the ventilator hoods for the magazines and tunnel network connecting the turrets.

A view from the western side of the island. The turrets are marked by the pale circles surrounding them.

From what I can see the fortifications underwent a major upgrade immediately before and during the First World War, the guns above probably replacing older and less potent ordinance. The two main turrets were sited at the highest point of the island, about 160 feet above sea level. What with this and their low profiles, it would've made the turrets hard to hit by seaborne artillery and given the four guns a large measure of plunging fire capability. I believe there were smaller guns of around 4.1"/105mm calibre covering the harbour and anchorage.

All of the above pieces were dismantled following the 1918 Armistice. In the 1930s the Nazis evacuated the islanders and refortified Heligoland again, and the batteries were referred to as the Nordgrüppe. An extensive network of tunnels was constructed throughout the island to link most of the gun positions, which now included a sizable AA component. It was intended to base a number of U-Boats on Heligoland. Although one pen was built to house the submarines the plan was scaled down when French bases became available after 1940.

Britain took control of Heligoland again in 1945, and again it was decided to demolish the fortifications. In one of those rather bizarre experiments that followed the Second World War, the British Army took one third of the surplus explosives left after the war and packed it all into the tunnel system. They then touched it all off at once...

Bang.

In the scale of things the explosion is rated as the largest non-nuclear event in history, with roughly one third the power of the Hiroshima bomb. Some predicted that Heligoland would be obliterated. As it was, the poor little island shook down to its roots and the eastern third collapsed. As if that wasn't enough, the RAF used Heligoland as a bombing range up to 1952, at which time Britain handed over what was left of it to then-West Germany.

(Thankfully the island is at peace now. The collapsed eastern half was leveled and a new community with harbor facilities built on the site, although the craters left from wartime and subsequent bombing are still visible on the top of the island. One part of the old above-ground fortifications remains: In 1952 a former WW2 flak tower was converted to create the island's lighthouse. Due to Heligoland's no cars policy, a lack of significant vegetation to create pollen, and the mild climate, it's a good place for people with allergies and respiratory ailments to visit. It also features an almost unique duty-free economy, and a world recognised guillemot sanctuary on the western cliffs).

So, some interesting features to consider in a naval campaign. Situated some 43 miles from the mainland the island was an effective outwork for the German naval bases and ports of Hamburg, Cuxhaven, Bremerhaven and Wilhelmshaven around the shores of the German Bight. By the same criteria it also made a potential blocker for the same.

At roughly half a mile long and a quarter mile wide it's not too big to represent Heligoland on the table in 1/2400 scale since (unless my math is off - which is entirely possible) it'll be about 13 inches long.

A few weeks ago, Peter at Grid based Wargaming played out his St. Nazaire raid project using simple but effective scratch-built buildings, emplacements and landing craft. A similar approach would work well for a hypothetical attack on Heligoland. Hmm...