It became a symbol of brutal German aggression - an unprovoked torpedo attack on a passenger cruise liner during the First World War. The infamous sinking of the Lusitania in 1915, killing more than 1,000 innocent victims, sparked outrage in Britain and America. Public opinion in the States swung against the Kaiser - eventually helping President Woodrow Wilson take the country into the war in 1917. But 70 years after the ship was torpedoed . by a German U-boat eight miles off the coast of Ireland, British Government officials feared the secret of . the tragedy would 'blow up on us' when a group of . divers planned to search the wreck. The sinking of the Lusitania off the coast of Ireland after being torpedoed by a German U-boat proved a major turning point in the war . The unprovoked attack on the Lusitania sparked outrage in Britain, Ireland and America. But the Germans always insisted that the ship was packed with explosives from the States destined for the Western Front . The German high command always maintained the steam liner, traveling between New York and Liverpool, was carrying explosives destined for the Western Front concealed as cheese or casks of beef. But ministers at the time rejected the claim and used the attack to whip up public anger against the Germans. 'Take up the sword of justice – avenge the Lusitania' read one famous poster. The campaign was used effectively in Ireland, where conscription was not compulsory. However, secret government documents released under the 30-year-rule this week reveal that the German claims may have been right all along. After salvage companies applied to raise the 790ft Cunard liner in 1982, the Government fired off warnings about danger to life, according to the National Archives documents. The sinking was a tragedy for more than a 1,000 men, women and children who died - but it was used relentlessly by the British Government to convince Irish and American sceptics to help defeat 'the hun'. Irish men were urged to  'take up the sword of justice - avenge the Lusitania' amid widespread public disgust over the torpedo attack. A series of posters were produced featuring pictures of the dramatic scene. American fury over the attack swung public opinion firmly onto the side of the allies - and against the Germans. This helped President Woodrow Wilson take the US into the war in 1917. Officials feared attempts to survey the wreck would reveal an illegal stash of ammunition - discrediting one of the key reasons why the the Americans were dragged into the war. Files show that the Ministry of Defence even went as far as warning divers that the wreck could contain explosives. Foreign and Commonwealth Office files show that officials feared the controversy would 'literally blow up on us' denting Britain's special relationship with the US. There were also concerns that American survivors and relatives of those who died could sue the Government. In a secret memo, Noel Marshall, from the Foreign Office's North American department, said: 'Successive British governments have always maintained that there was no munitions on board the Lusitania (and that the Germans were therefore in the wrong to claim to the contrary as an excuse for sinking the ship). 'The facts are that there is a large amount of ammunition in the wreck, some of which is highly dangerous.' He added: 'I am left with the uneasy feeling that this subject may yet - literally - blow up on us.' The Lusitania was steaming from New York to Liverpool when she was hit by the German submarine U-20 on May 7, 1915. The . explosives, after being hit by the German torpedo, sparked a larger . blast causing the giant liner -  a sister ship of the Titanic - to sink . in just 18 minutes. The Government has admitted that there were 4,200 'small arms' cartridges and ammunition cases on the ship - and these were declared at the time. But they were not classified as 'ammunition'. Experts claim these could not have been responsible for the second giant explosion which sunk the liner. A senior government lawyer, Jim Coombes, warned there could still be a political scandal if it was found that there had actually been explosives on board. 'It cannot be denied that the sinking of the Lusitania did much to sway American opinion in favour of entering the war,' he wrote. 'If it were now to come to light that there was after all some justification, however slight, for the torpedoing, HMG's relations with America could well suffer.' The UK's relationship with America was crucial in 1982 - at the height of the Cold War. It was also the year in which British troops marched into Port Stanley in the Falklands War. Margaret Thatcher and Ronald Reagan, pictured here in 1982, were Cold War allies. Britain could not risk damaging the relationship at this time by allowing revelations to emerge that the Lusitania had been piled high with explosives . Destined for Liverpool after setting sail in New York, the Lusitania sank in just 18 minutes eight miles off the coast of Ireland . William Turner, captain of the Lusitania. He survived the attack which killed more than 1,000 civilians . Among those who died in the tragedy included politicians, artists, academics and businessmen, as well as the art collector, Sir Hugh Lane, who is said to have been carrying paintings by Titian, Monet and Rubens in sealed containers. Since 1982, there have been a number of dives and surveys of the wreck, including one in 2012 which found no evidence of any high explosives and concluded the second blast reported by some of the 761 survivors was one of the ships boilers exploding. However the wreck’s owner, Gregg Bemis, an entrepreneur, from New Mexico, who has been trying for 40 years to find out if the ship had a secret military cargo, has asked the Irish Government to sanction further dives to prove his theory. In 1918 a New York judge had ruled that there were 4,200 cases of safety cartridges, 18 fuse cases and 125 shrapnel cases without any powder charge on board the liner when it went down. But he ruled that these did not constitute 'war munitions'. He added that the Lusitania had not been armed or carried any high explosives. The 1915 British inquiry into the sinking of the Lusitania, chaired by Lord Mersey, barely touched on the issue. But when a French survivor, Joseph Marichal, a former army officer, claimed that the ship had sunk so quickly because of a second explosion, his testimony was quickly dismissed. Mr Marichal, who had been in the second-class dining room, said the explosion was 'similar to the rattling of a maxim gun for a short period' and came from underneath the whole floor. But Lord Mersey said: 'I do not believe him. His demeanour was very unsatisfactory. There was no confirmation of his story.'
Cruise liner RMS Lusitania sunk by a German u-boat in May 1915 .
More than 1,000 men, women and children died in the tragedy .
Germans claimed it was carrying explosives destined for the frontline .
Incident used as a recruiting tool by British army, particularly in Ireland .
Also proved crucial in persuading the US to join the war effort .
It became a symbol of brutal German aggression - an unprovoked torpedo attack on a passenger cruise liner during the First World War. The infamous sinking of the Lusitania in 1915, killing more than 1,000 innocent victims, sparked outrage in Britain and America. Public opinion in the States swung against the Kaiser - eventually helping President Woodrow Wilson take the country into the war in 1917. But 70 years after the ship was torpedoed . by a German U-boat eight miles off the coast of Ireland, British Government officials feared the secret of . the tragedy would 'blow up on us' when a group of . divers planned to search the wreck. The sinking of the Lusitania off the coast of Ireland after being torpedoed by a German U-boat proved a major turning point in the war . The unprovoked attack on the Lusitania sparked outrage in Britain, Ireland and America. But the Germans always insisted that the ship was packed with explosives from the States destined for the Western Front . The German high command always maintained the steam liner, traveling between New York and Liverpool, was carrying explosives destined for the Western Front concealed as cheese or casks of beef. But ministers at the time rejected the claim and used the attack to whip up public anger against the Germans. 'Take up the sword of justice – avenge the Lusitania' read one famous poster. The campaign was used effectively in Ireland, where conscription was not compulsory. However, secret government documents released under the 30-year-rule this week reveal that the German claims may have been right all along. After salvage companies applied to raise the 790ft Cunard liner in 1982, the Government fired off warnings about danger to life, according to the National Archives documents. The sinking was a tragedy for more than a 1,000 men, women and children who died - but it was used relentlessly by the British Government to convince Irish and American sceptics to help defeat 'the hun'. Irish men were urged to  'take up the sword of justice - avenge the Lusitania' amid widespread public disgust over the torpedo attack. A series of posters were produced featuring pictures of the dramatic scene. American fury over the attack swung public opinion firmly onto the side of the allies - and against the Germans. This helped President Woodrow Wilson take the US into the war in 1917. Officials feared attempts to survey the wreck would reveal an illegal stash of ammunition - discrediting one of the key reasons why the the Americans were dragged into the war. Files show that the Ministry of Defence even went as far as warning divers that the wreck could contain explosives. Foreign and Commonwealth Office files show that officials feared the controversy would 'literally blow up on us' denting Britain's special relationship with the US. There were also concerns that American survivors and relatives of those who died could sue the Government. In a secret memo, Noel Marshall, from the Foreign Office's North American department, said: 'Successive British governments have always maintained that there was no munitions on board the Lusitania (and that the Germans were therefore in the wrong to claim to the contrary as an excuse for sinking the ship). 'The facts are that there is a large amount of ammunition in the wreck, some of which is highly dangerous.' He added: 'I am left with the uneasy feeling that this subject may yet - literally - blow up on us.' The Lusitania was steaming from New York to Liverpool when she was hit by the German submarine U-20 on May 7, 1915. The . explosives, after being hit by the German torpedo, sparked a larger . blast causing the giant liner -  a sister ship of the Titanic - to sink . in just 18 minutes. The Government has admitted that there were 4,200 'small arms' cartridges and ammunition cases on the ship - and these were declared at the time. But they were not classified as 'ammunition'. Experts claim these could not have been responsible for the second giant explosion which sunk the liner. A senior government lawyer, Jim Coombes, warned there could still be a political scandal if it was found that there had actually been explosives on board. 'It cannot be denied that the sinking of the Lusitania did much to sway American opinion in favour of entering the war,' he wrote. 'If it were now to come to light that there was after all some justification, however slight, for the torpedoing, HMG's relations with America could well suffer.' The UK's relationship with America was crucial in 1982 - at the height of the Cold War. It was also the year in which British troops marched into Port Stanley in the Falklands War. Margaret Thatcher and Ronald Reagan, pictured here in 1982, were Cold War allies. Britain could not risk damaging the relationship at this time by allowing revelations to emerge that the Lusitania had been piled high with explosives . Destined for Liverpool after setting sail in New York, the Lusitania sank in just 18 minutes eight miles off the coast of Ireland . William Turner, captain of the Lusitania. He survived the attack which killed more than 1,000 civilians . Among those who died in the tragedy included politicians, artists, academics and businessmen, as well as the art collector, Sir Hugh Lane, who is said to have been carrying paintings by Titian, Monet and Rubens in sealed containers. Since 1982, there have been a number of dives and surveys of the wreck, including one in 2012 which found no evidence of any high explosives and concluded the second blast reported by some of the 761 survivors was one of the ships boilers exploding. However the wreck’s owner, Gregg Bemis, an entrepreneur, from New Mexico, who has been trying for 40 years to find out if the ship had a secret military cargo, has asked the Irish Government to sanction further dives to prove his theory. In 1918 a New York judge had ruled that there were 4,200 cases of safety cartridges, 18 fuse cases and 125 shrapnel cases without any powder charge on board the liner when it went down. But he ruled that these did not constitute 'war munitions'. He added that the Lusitania had not been armed or carried any high explosives. The 1915 British inquiry into the sinking of the Lusitania, chaired by Lord Mersey, barely touched on the issue. But when a French survivor, Joseph Marichal, a former army officer, claimed that the ship had sunk so quickly because of a second explosion, his testimony was quickly dismissed. Mr Marichal, who had been in the second-class dining room, said the explosion was 'similar to the rattling of a maxim gun for a short period' and came from underneath the whole floor. But Lord Mersey said: 'I do not believe him. His demeanour was very unsatisfactory. There was no confirmation of his story.'
torpedoed by a German U-boat proved a major Liverpool, was carrying explosives destined for a tragedy for more than a 1,000 men, women and children who died - but it was used relentlessly President Woodrow Wilson take the US into the war the Lusitania (and that the Germans were those who died in the tragedy included