Tag Archives: 280mm gun

The eerie quiet before the end, 74 years ago

Pre-Surrender Nocturne Tokyo Bay.”

Painting, Watercolor on Paper; by Standish Backus; 1945. Depicting the old forts at Futtsu Saki, a narrow point of land jutting into the eastern side of Uraga Strait at the entrance to Tokyo Bay, a burnt-out Japanese destroyer, and the eeriness of the moonlight:

(NHHC: 88-186-Z)

The artist’s notes:

The forts at Futtsu Saki had to be approached and demobilized early on the morning of 30 August 1945. No landings from the sea had yet occurred and we did not know what sort of reception we would receive from the Japanese. From past experience, it was not expected to be healthy in all respects. Was there a division of troops in those forts waiting to mow us down as we hit the beach? Its very silence, the haunted quantity of the burnt-out Japanese destroyer, and the eeriness of the moonlight gave us all a foreboding.

The forts were, in fact, well-defended, by a full regiment but the artillery on hand was old. One of the first coastal defense forts in the country, the batteries used 15cm Krupp guns in steel cupolas and several emplaced Model 1890 Osaka-made (Armstrong-Whitworth designed) 28cm howitzers that the Japanese had at least twice dismounted and used as siege guns (at both Port Arthur and Tsingtao) back when they were still relevant.

Japan coast defense 280mm L/10 howitzers nicknamed “Osaka Babies” by the Japanese and “Roaring Trains” by the Russians when they were dismounted and used as siege artillery at Port Arthur in 1904. While dated, these beasts could still ruin a ship that came within their reach. 

It was a pucker factor for sure.

As related by Backus in his painting “The First Wave on Japan”

Watercolor on Paper; by Standish Backus; 1945; Unframed Dimensions 16H X 23W. (NHHC: 88-186-B)
“Futtsu Peninsula, Tokyo Bay: Seal-like Higgins boats create their own heavy seas as they carry Marines of the 2nd Battalion 4th Regiment ashore for the first test of whether the Japanese will resist or abide by negotiated surrender terms. It is tense for the next five minutes. The Japanese would logically wait until the Marines were at the shoreline to open a withering fire that could be a massacre. Since there could be no preparatory bombing or bombardment, it had to be done the hard way by head-on assault. The main group of boats landed here at Fort #2 while a small group landed at Fort #1 at the end of the spit beyond the hulk of a burned-out Japanese destroyer. The setting moon, which stood watch over the landing of the boats from the transport, is now relieved by the misty rays of the early sun.”

But the Forts were captured with no bloodshed on either side.

The first landing craft carrying Marines of 2/4 touched the south shore of Futtsu Saki at 0558; two minutes later, the first transport plane rolled to a stop on the runway at Atsugi, and the occupation of Japan was underway. In both areas, the Japanese had followed their instructions to the letter. On Futtsu Saki the coastal guns and mortars had been rendered useless, and only the bare minimum of maintenance personnel, 22 men, remained to make a peaceful turnover of the forts and batteries. By 0845, the battalion had accomplished its mission and was reembarking for the Yokosuka landing, now scheduled for 0930.

Members of the Yokosuka Occupation Force, 2/4 Marines, inspect a Japanese fortification on Futtsu Saki. [USMC 134741]. Besides the Marines, the landing force was accompanied by 10 U.S. Navy gunners mates familiar with large naval pieces to disable the captured guns. 

The 280mm M65 Atomic Cannon

On May 25, 1953 a 280mm M65 Atomic Cannon operated by the United States Army was tested at the Nevada Test Site as part of the Upshot-Knothole series of nuclear tests. The test resulted in the successful detonation of a 15 kt shell (warhead W9) at a range of 7 miles. Although missile technology and other methods of delivering atomic warheads were already well advance, the Army still manufactured at least 20 of these cannons which were deployed to locations in Europe and Korea. The 280mm cannons were retired from service in 1963.

Test Grable was the second of only four gun-type warheads ever detonated (the first was Little Boy, the weapon used against Hiroshima, the last two were test firings of the W33; all other atomic weapons were implosion-type weapons). The shell, designated a Mark 9 nuclear weapon, had a diameter of 280 mm (11.02 in), was 138 cm (54.4 in) long and weighed 364 kg (803 lb). The M65 Atomic Cannon from which it was fired had a muzzle velocity of 625 m/s (2,060 ft/s), for a nominal range of 32 km (20 mi), and weighed 77 metric tons (85 t).

The detonation of Grable occurred 19 seconds after its firing. It detonated over 11,000 yards (over 10 km, 6.25 mi) away from the gun it was fired from, over a part of the Nevada Test Site known as Frenchman Flat. The explosion was an air burst of 160 m (524 ft) above the ground (7 m (24 ft) above its designated burst altitude), 26 m (87 ft) west and 41 m (136 ft) south of its target (slightly uprange). Its yield was estimated at 15 kilotons, around the same level as Little Boy. An anomalous feature of the blast was the formation of a precursor, a second shock front ahead of the incident wave. This precursor was formed when the shock wave reflected off the ground and surpassed the incident wave and Mach stem due to a heated ground air layer and the low burst height. It resulted in a lower overpressure, but higher overall dynamic pressure, which inflicted much more damage on drag sensitive targets such as jeeps and personnel carriers. This led strategists to rethink the importance of low air bursts in tactical nuclear warfare.

Further information about the M65 Atomic Cannon be be found at http://en.wikipedia.org/wiki/M65_Atomic_Cannon

This film was produced by the United States Air Force on behalf of the Department of Energy.