French battleship Iéna

Like the Charlemagne-class ships, Iéna carried her main armament of four 40-calibre Canon de 305 mm (12 in) Modèle 1893–1896 guns in two twin-gun turrets, one each fore and aft of the superstructure. Each turret had a dedicated 300-ampere dynamo to traverse it and to power the ammunition hoist. The guns, however, were manually elevated between their limits of −5° and +15°, and they were normally loaded at an angle of −5°. The guns fired 340-kilogram (750 lb) armour-piercing, capped (APC) projectiles at the rate of one round per minute at a muzzle velocity of 815 m/s (2,670 ft/s).[9] This gave a range of 12,000 metres (13,000 yd) at the maximum elevation of +15°. The magazines stored 45 shells per gun,[3] and an additional 14 projectiles were stowed in each turret.[9]

The ship's secondary armament consisted of eight 45-calibre Canon de 164.7 mm Modèle 1893 guns, which were mounted in the central battery on the upper deck,[3] and fired 54.2-kilogram (119 lb) APC shells. At their maximum elevation of +15°, their muzzle velocity of 800 m/s (2,600 ft/s)[10] gave them a maximum range of 9,000 metres (9,800 yd). Each gun was provided with 200 rounds, enough for 80 minutes at their sustained rate of fire of 2–3 rounds per minute.[11] She also carried eight 45-calibre Canon de 100 mm (3.9 in) Modèle 1893 guns in single, unprotected, mounts on the shelter deck. These guns fired a 14-kilogram (31 lb) projectile at 740 m/s (2,400 ft/s),[12] which could be trained up to 20° for a maximum range of 9,500 metres (10,400 yd). Their theoretical maximum rate of fire was six rounds per minute, but only three rounds per minute could be sustained.[3] Each gun was provided with 240 shells in the ship's magazine.[13]

Iéna's anti-torpedo boat defences consisted of twenty 40-calibre Canon de 47 mm (1.9 in) Modèle 1885 Hotchkiss guns, fitted in platforms on both military masts, embrasures in the hull, and in the superstructure.[8] They fired a 1.49-kilogram (3.3 lb) projectile at 610 m/s (2,000 ft/s) to a maximum range of 4,000 metres (4,400 yd). Their theoretical maximum rate of fire was fifteen rounds per minute, but only seven rounds per minute sustained. The ship's magazines held 15,000 shells for these guns.[14] Rear-Admiral (Contre-amiral) René Marquis criticised the arrangements for the 47 mm guns in a 1903 report: "The number of ready-use rounds is insufficient and the hoists are desperately slow. The 47 mm guns, much more so than the large and medium-calibre guns, will have to fight at night; yet these are the only guns without a fire-control system designed for night operations. This is a deficiency which needs to be corrected as soon as possible."[15] Iéna also mounted four 450-millimetre (17.7 in) torpedo tubes, two on each broadside, one submerged and the other above water. The submerged tubes were fixed at a 60° angle from the centreline and the above-water mounts could traverse 80°.[16] Twelve Modèle 1889 torpedoes were carried, of which four were training models in peacetime.[14]

The ship had a complete waterline belt of Harvey armour that was 2.4 metres (7 ft 10 in) high. The armour plates were 320 mm (12.6 in) thick amidships; they thinned to a thickness of 272 mm (10.7 in) at the bow and 224 mm (8.8 in) at the stern. Below the waterline, the plates tapered to a thickness of 120 mm (4.7 in) at their bottom edge for most of the ship's length although the plates at the stern were 100 mm thick. The upper armour belt was in two strakes, the lower 120 mm thick and the upper 80 mm (3.1 in). Their combined height was 2 metres (6 ft 7 in) amidships. The lower strake was backed by a highly subdivided cofferdam intended to reduce flooding from any penetrating hits as its compartments were filled by 14,858 water-resistant "bricks" of dried and compressed Zostera seaweed (briquettes de zostère). The seaweed was intended to expand upon contact with water and plug any holes. The armoured deck consisted of a 65 mm (2.6 in) mild steel plate laid over two 9 mm (0.35 in) plates. The splinter deck beneath it comprised two layers of 17 mm (0.67 in) plates.[17]

The Harvey armour plates protecting the sides of the turrets were 290 mm (11.4 in) in thickness and the mild steel of the turret roofs was 50 mm (2 in) thick. The barbettes were protected by 250 mm (9.8 in) of Harvey armour. The sides and rear of the central battery were 90 mm (3.5 in) thick. The forward transverse bulkhead ranged in thickness from 55–150 millimetres (2.2–5.9 in), the thicker plates protecting the central battery, and reduced in thickness the further down it went until it met the armoured deck. The 164 mm guns were protected by 70-millimetre (2.8 in) gun shields. The armour plates protecting the conning tower ranged in thickness from 258 to 298 mm (10.2 to 11.7 in) on its face and rear, respectively. Its communications tube was protected by 200 mm (7.9 in) of armour.[18]

A postcard showing the amidships portion of Iéna, with charred and scorched paint prominent

On 4 March 1907 Iéna was moved into Dry dock No. 2 in the Missiessy Basin at Toulon to undergo maintenance of her hull as well as an inspection of her leaking rudder shaft. Eight days later, beginning at 13:35 and continuing until 14:45, a series of explosions began near the aft 100-millimetre magazines which devastated the ship and the surrounding area. The explosions blew the roofs off three nearby workshops and gutted the area between the aft funnel and the aft turret. Because the ship was in a dry dock with the water pumped out, it was initially impossible to flood the magazines, which had not been unloaded before docking. The commanding officer of the battleship Patrie, which was moored nearby, fired a shell into the dry dock gates in an attempt to flood it, but the shell ricocheted without holing the gate. They were manually opened shortly afterwards by one of the ship's officers. A total of 118 crewmen and dockyard workers were killed by the explosions, as were 2 civilians in the suburb of Pont-Las who were killed by fragments.[24]

Inauguration of the monument to the victims of the explosion, 1908

On 17 March, the President of France, Armand Fallières, and Georges Clemenceau, who was both the President of the Council of Ministers and Minister of the Interior attended the funeral of those lost during the explosion. A national day of mourning was declared and a monument was built in the cemetery of Lagoubran. Both houses of the French Parliament, the Senate and the Chamber of Deputies, organised commissions to inquire into the cause of the explosion. The Senate appointed its commission on 20 March under the chairmanship of Ernest Monis; the Chamber of Deputies followed eight days later with Henri Michel as chair.[25]

The origin of the first explosion was traced to a 100 mm magazine and was believed to have been caused by decomposing Poudre B, a nitrocellulose-based propellant, which tended to become unstable with age and self-ignite, though a report published in April 1907 stated a torpedo exploded in the torpedo room directly below the magazine.[26] When burnt, it gave off yellow-coloured smoke, which matched the colour seen by eye-witnesses. To test this theory, Gaston Thomson, the Navy Minister, ordered on 31 March that a replica magazine and the adjacent black-powder magazine be built, but when the tests were conducted on 6–7 August, they were deemed inconclusive because the propellant used in the test was not of the same age as that aboard Iéna. Fallières appointed a technical commission on 6 August that included mathematician Henri Poincaré, chemist Albin Haller and the inventor of Poudre B, Paul Vieille, that failed to come to a definite conclusion. The navy's Propellant Branch (Service des Poudres et Saltpêtres) objected to the criticisms of its product, claiming that it was tested to resist 43 °C (110 °F) temperatures for 12 hours, although it never explained how that test was relevant to the long-term storage of Poudre B in magazines limited to natural ventilation, as was used by every ship in the fleet.[27] The Monis Commission published its report on 9 July, blaming the explosion on Poudre B, and was debated on 21–26 November. The Michel Commission published its report on 7 November 1908, although its contents had been debated on 16–19 October, and was "a model of vagueness and imprecision".[28] The reason for the explosion became a cause célèbre with accusations of gross negligence by the government such that Thomson was forced to resign on the last day of the debate.[29]

The multiple explosions ripped open the ship's side between Frames 74 and 84 down to the lower edge of the armour belt, and all the machinery in this area was destroyed. After it was estimated that it would take seven million francs and two years to fully repair Iéna, which was already obsolete, the navy decided to decommission her and use her as a target ship. The ship was stricken from the navy list on 18 March and her crew was reassigned on 3 July. Iéna was disarmed, except for her 305 mm guns, and all useful equipment was removed in 1908. She was rendered seaworthy again at a cost of 700,000 francs and was towed to a mooring off the Île des Porquerolles. A programme to evaluate the effectiveness of Melinite-filled armour-piercing shells began on 9 August 1909 with the armoured cruiser Condé firing projectiles from her 164.7 mm and 194 mm (7.6 in) guns at a range of 6,000 metres (6,600 yd). After every shot the results were photographed and the effects on the crew of wooden dummies and live animals evaluated. By 2 December Iéna was close to foundering and the navy decided to have her towed to deeper water. Shortly after the tow began, she capsized and sank in shallow water. The rights to the wreck were sold on 21 December 1912 for 33,005 francs and she was slowly broken up and salvaged between 1912 and 1927. Another company was contracted to remove the remnants of the wreck in 1957.[30]