In 2011, a team of divers operating off the Swedish Island of Oland found the wreck of a large warship. From artefacts recovered from the site, she was positively identified as the Mars, pride of the Swedish navy, which had been sunk in 1564. Lying in seventy-five metres of brackish water in the virtually tide-free Baltic she was astonishingly well preserved. After four and half centuries, her stern quarter appeared almost as if the shipwrights that built her had only just completed their work. But a fan of her timbers that radiated out across the dark sea floor hinted at the catastrophic explosion that had sent her to the bottom.
The Mars was claimed to be the largest warship in the Baltic at the time of her construction. She was built in Bjorkenas in Sweden, a shipyard that has since disappeared beneath woods and meadows, between 1561 and 1563. Her hull was 53 metres long, and she carried over a hundred cannon. By comparison Henry VIII’s Mary Rose, which sunk twenty years earlier, was barely half her size. The Mars was a great ship, designed to awe Sweden’s opponents. A year after she was completed, she was leading the Swedish fleet into battle.
The 16th century was a time of shifting power in Scandinavia. Denmark had been the dominant power in the region, but was in relative decline vs. the newly emerging Sweden. Rising tensions between the two countries led to the outbreak of the Northern Seven Years War in 1563. The following year the Swedish fleet of thirty five warships clashed with a similar sized fleet of combined Danish and Lubeck vessels off the island of Oland.
Naval actions in this period were rarely decisive, and the Battle of Oland was no exception. In medieval times battles at sea were essentially fought as if the participants were on land. Both sides would load their ships with soldiers, and defeat their opponents by boarding. In the late 15th century this started to change with the introduction of heavy cannon, but by 1564 naval gunnery was still a technology in its infancy. Guns were fragile and prone to burst, making any sort of live fire training prior to battle too dangerous. They also lacked the gun tackles and bagged powder charges of later centuries that might have permitted them to be fired rapidly. Cannon had to reloaded by crewmen hanging out of gun ports and ladling loose powder down their barrels. The result was a very slow rate of fire, and often hazardous trails of loose powder on the deck.
At Oland the ships of the rival fleets skirmished with each other over two days, but light winds hampered either side from coming to grips with their opponent. Then, on the second day, the Swedish flagship Mars, found herself isolated and surrounded by three of the enemy’s ships. After an exchange of broadsides, the Mars was boarded by a swarm of opponents who swept clear her upper deck, capturing Jakob Bagge, the Swedish commander. As the fighting spread to the lower decks of the Mars, her timbers caught fire and, doubtless aided by the trails of loose powder on her gun decks, this spread rapidly. When the flames reached her magazine, she exploded, taking most of her crew, together with over three hundred enemy boarders, to the bottom of the Baltic.
Both sides broke off the action soon afterwards, retreating to Stockholm and Copenhagen respectively. No one had noted with any precision where the Mars had sunk, and in any event she lay in waters far too deep to be dived in until comparatively recently. As a result, her wreck lay in complete darkness, on the sea floor, for almost half a millennia. There are almost no tides and few currents in the Baltic to disturb her, so she was preserved in the brackish water until her oak timbers appeared again, in the silver beam of light held by a diver.