The Mars warship was carrying hundreds of soldiers when it exploded in the Baltic Sea in 1564 during the Northern Seven Years’ War. 
 
 Cannons, hand grenades, and up to a thousand soldiers were on board the large Swedish warship when it exploded in the Baltic Sea, 454 years ago. 
 
 The ship, known as Mars, belonged to the Swedish navy and was one of Northern Europe’s largest and most feared naval vessels used in the Northern Seven Years’ War. 
 
 The remains were discovered at the bottom of the Baltic Sea in 2011, near to the Swedish island of Öland. 
 
 The latest discoveries from the wreckage were revealed during a press conference in Öland. 
 
 “This year, we have come closer to the people aboard. We found more skeletal parts, including a femur with trauma around the knee which we believe to stem from a sharp-edged weapon,” says maritime archaeologist Rolf Fabricius Warming, who is one of the researchers involved in the investigation. 
 
 “We also found large guns and a hand grenade. We can see from the wreckage that it was a very intense and tough battle. Between 800 and 1,000 men were on board. That is comparable to the population of an entire medium-sized town at the time. Most of them died in the explosion or when the ship sank into the watery depths,” he says. 
 
 Read More: Researchers discover remains of sunken Swedish warship 
 
 The ship contained silver treasure 
 
 Researchers had previously discovered silver treasure among the Mars wreckage. This time, one of the most spectacular finds was a large grapnel (grappling hook) an anchor-like hook, which hung from the bowsprits of warships and was used to cling onto another ships in order to board it. 
 
 Grapnels are illustrated in historical sources from the 16th century, but no actual surviving examples are known apart from this particular one, says Warming. 
 
 “It’s totally unique. Together with other exciting finds, it can shed new light on Medieval and Early Modern naval warfare. ,” he says, and adds that the divers also found remains of possible arms and armour, including helmets and swords. 
 
 Read More: The Viking’s grave and the sunken ship 
 
 Danish and Lübeckian soldiers were on board 
 
 Mars sunk due to a gunpowder explosion at the front of the ship. But shortly before, it had been under attack by Danish and Lübeckian warships according to written sources. 
 
 “Soldiers fought with hand grenades, lances, and spears, which they threw down from the masts. The fighting was structured and carefully calculated but an absolute ruckus” says Warming. 
 
 Danish soldiers, allied with soldiers from Lübeck, managed to defeat the Swedish crew and capture the warship. When the ship exploded and sank, it had three to four hundred Dano-Lübeckian soldiers aboard. 
 
 A 3D- model of the shipwreck. (Video: Ocean Discovery / Ingemar Lundgren) 
 
 A Swedish change of tactics 
 
 The new examination of the Mars shipwreck provides new insights into the events that took place between Denmark and Sweden during the Northern Seven Years’ War between 1563 and 1570. 
 
 They have documented a change in Swedish tactics from a focus on close quarter combat to long distance fighting, as indicated by large cannons up to 4.8 metres long. 
 
 Despite the large cannons, the Swedish crew did not manage to avoid engaging in close quarter combat with their enemies. The soldiers aboard were positioned underneath a net that covered the deck and was designed to prevent the enemy from jumping on board – a so-called anti-boarding net. 
 
 “We know about the use of anti-boarding nets in this battle from richly detailed written sources. The Swedish Admiral, Jacob Bagge, describes in his own account of the battle how he was injured in the shoulder by a javelin thrown from one of the fighting tops of the enemy ships. t. We are told he became furious and began shooting at those who had injured him with arquebuses so that they fell into the net below,” says Warming. 
 
 Read More: Medieval shipwreck hints at psychological warfare 
 
 A snapshot of a moment in time 
 
 Until 2011, historians relied on written sources for information about what happened to Mars, including letters from the Danish admiral Herluf Trolle and the Swedish admiral Jacob Bagge, and official royal documents. 
 
 But the shipwreck provides an entirely different type of documentation. 
 
 “There’s some ‘fake news’ in the written sources. Many people wanted to claim the honour of defeating the Mars for various political reasons. But when we study the wreckage itself we see a large congruency between the wreck site and the historical sources. One of the most striking observations was that it really was sunk by a large explosion. It was so violent that the front of the ship lies 40 metres away from the other remains,” says Warming. 
 
 For maritime archaeologist Mikkel Thomsen from the Viking Ship Museum, Denmark, looking at the well preserved, and complete remains captures a snapshot of a moment in time. 
 
 “You really feel that you’re in the killing fields,” says Thomsen, who was not involved in the study. 
 
 “The wreckage gives a snapshot of a piece of military and political history. It’s also an international history as the Seven Years’ War was fought across national boundaries,” he says. 
 
 Read More: Historic shipwrecks could be preserved in the Antarctic 
 
 Divers filmed the shipwreck 
 
 The Mars remains lay 70 metres beneath the surface of the Baltic Sea—so deep that researchers could not go down themselves to investigate. Instead, professional divers and ROVs were deployed to film the wreck. 
 
 The footage and recordings were used to create 3D-models of the wreck and the artefacts found on the site. 
 
 Scientists and divers have not been granted permission to touch or remove anything from the wreck or nearby, which might be for the best, according to Thomsen. 
 
 “The Baltic Sea has extremely good preservation conditions. The water is low in oxygen, cold, and fresh. So boring worms that are usually the greatest threat to wood cannot live there,” says Thomsen. 
 
 Lifting the remains out of the water would lead to breakdown and damage of the materials, he says. 
 
 “Moreover, it would be very difficult and extremely expensive to retrieve it from such deep water,” says Thomsen. 
 
 The exploration of Mars was carried out by researchers from the Marine Research Institute MARIS at Södertörn University in Sweden, and divers from the diving organization GUE, Västervik Museum, Ocean Discovery, and MMT. 
 
 Fifteen divers and ten researchers have participated in the latest exploration of the ship. 
 
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 Read the original article in Danish at Videnskab.dk ||||| Kronan The 126 gun battleship Kronan was built in 1668 by Francis Sheldon and was one of the world's largest ships in its time. She was 53 m long and 14 m wide. During battle against a Danish-Dutch fleet in June 1676, Kronan listed heavily during a badly prepared turn, then suddenly exploded and quickly sank with 800 men. Only 42 survived. What caused the blast is a mystery, perhaps something broke loose during the list and ignited the gunpowder. Possibly Lorentz Creutz, the newly appointed commander and admiral, is to blame for incompetence, because he had no naval experience before commanding the ship. Discovery This was one of the lost wrecks that engineer/archaeologist Anders Franzén found in Swedish archives and placed on a search list. Finally, Franzén together with Bengt Grisell and Sten Ahlberg found the ship in 1980 off Öland in the south Baltic Sea on 27 m depth. The hull is broken apart but a large section of the port shipside is intact and laying with the outside facing the bottom clay. This will possibly be salvaged in the future. Bronze guns Already shortly after the sinking, between 1680 and 1686, 60 guns were salvaged using primitive dive bells, and then the ship was forgotten for centuries. But the old divers only got half of the guns. Originally, she had between 124 and 128 bronze guns. So fortunately the wreck has remained a gold mine for bronze guns. Between 1980 and '87 another 32 guns have been salvaged. They are in sizes from 6 to 36 pounds, and cast between 1514 and 1661. Some of them may well have come from the Vasa, sunk in 1628. The oldest gun, from 1514, is the oldest known muzzle-loaded gun in Scandinavia. Investigations This has become the largest underwater archaeology project in Sweden. Initiated in 1981 and will continue a few more seasons. Plenty of well-preserved objects have been excavated so far. Among the finds are about 400 kg bones from the victims. These remains have been investigated by the osteologist Ebba During. During 1982-83 a cask with ca 260 gold coins was found – that's the largest gold coin treasure ever found in Sweden. In 1998 a complete cross staff was found as well as a magnificent case of tin bottles. In 2001 a pharmacy chest was found, containing 70 bottles and medicine cans. Future The excavations will continue for a few more seasons. Then a decision has to be made whether to raise the entire shipside, now laying face-down on the bottom. Hopefully many of the decorations are still in position and well preserved. But such an operation will be very expensive, including conservation. More private donors and sponsors would be needed to proceed. The project is headed by Lars Einarsson. Contact Kalmar County Museum, tel +46-480-563 00, fax +46-480-563 32, for details. Recreational diving on the site is not permitted. Related text Clay pipes from the man-of-war Kronan, Arne Ĺkerhagen Related links The Kronan official website 
 
 Article in Maritime History Virtual Archives References Svenska Dagbladet 1 juli 2001 
 
 National Geographic, April 1989 
 
 Günter Lanitzki: Versunken in der Ostsee (1993) 
 
 Günter Lanitzki: Flaggschiff Kronan (Transpress VEB Verlag, Berlin, 1989) 
 
 Anders Franzén: HMS Kronan, the search for a great 17th century Swedish warship (KTH 1981) 
 
 IJNA 19.4 1990 
 
 19.4 1990 British Museum Encyclopaedia of Underwater and Maritime Archaeology 
 
 The impressive stern, interpreted by Axel Nelson, based on contemporary information. Contemporary painting of the blast by Danish artist Claus Möinichen. Skull and bronze guns in situ. Photo Bengt Grisell The Kronan wrecksite. The missing bow section is outlined with dotted lines. One of the finds during the 1996 season, a medicine cabinet. In 1997 this basket was excavated. It contained tobacco and spices. View the 2001 news graphic (400 kb), courtesy Svenska Dagbladet.
– Seven years after it was found, a 454-year-old shipwreck in the Baltic Sea is still revealing its treasures. Cannons, a hand grenade, possible remains of helmets and swords, and a large grappling hook used to rein in enemy ships are among recent discoveries aboard Mars, a Swedish warship that sank following a battle in 1564 with Danish and German soldiers, reports National Geographic. The battle was "an absolute ruckus," as archaeologist Rolf Fabricius Warming puts it to ScienceNordic, describing grenades, lances, and spears hurled from the tops of enemy ships at Mars. The vessel had an anti-boarding net, but as many as 400 enemy soldiers were among the 800 to 1,000 on board when a gunpowder explosion at Mars' bow sent it to rest 250 feet below the sea's surface near Öland. "It was so violent that the front of the ship lies [130 feet] away from the other remains," says Warming, noting any soldiers not killed in the explosion would have drowned. In the latest search of the untouched wreck by divers and underwater vehicles, "we have come closer to the people aboard," he adds. "We found more skeletal parts, including a femur with trauma around the knee which we believe to stem from a sharp-edged weapon." But it's the grappling hook Warming finds most exciting. He calls it "totally unique," noting no other examples from the 16th century exist, except in illustrations. The hook will remain where it lies, however, along with silver treasure previously found. Researchers haven't been granted permission to disturb the wreck, which lies in cold, low-oxygen water ideal for preserving wood. (Legend has it the ship was cursed.)