A desperate letter sent by army chief Lord Kitchener to Winston Churchill exactly 100 years ago has shown how unprepared Britain was at the outbreak of the First World War.

The letters written in August 1914, which have been unearthed for the first time, also reveal the 'shell crisis' that Britain faced and the tension that existed between the two war leaders at a critical time in the conflict.

In August 1914, Churchill was First Lord of the Admiralty, the civil and political head of the Royal Navy, and had at his disposal ten million rounds of ammunition.

Lord Kitchener was Secretary of State for War at the outbreak of the First World War and requested ten million rounds of ammunition from Winston Churchill, who was First Lord of the Admiralty

Lord Kitchener was rebuffed by the Churchill and the letters show the tension that existed between the pair

Kitchener was the Secretary of State for War and was head of the British Expeditionary Force that was fighting German troops on the French borders as part of the Battle of the Frontiers.

His face famously appeared on First World War recruitment posters with the slogan 'Lord Kitchener Wants You'.

With the Allied forces pushed back to Antwerp and quickly running out of supplies, Kitchener wrote to Churchill on August 27 - a day after the Battle of Le Cateau, where the BEF suffered 7,812 casualties and were forced to retreat - requesting his help.

In the letter on War Office headed notepaper, he wrote: 'I think you said ten million rounds would be available. It makes me shudder to think of troops without ammunition.

'May I send an officer to the Admiralty to talk to your people about this and take over your contribution to Antwerp?'

But Kitchener was rebuffed by the future prime minister.

In his reply, Churchill wrote: 'No, no, no, no. 10,000,000 rounds is all I have got for the fleet.

'I have already given 500,000 rounds.

'I will see if anything can be scraped up from the ships to enable me to dispense with the 2,000,000 rounds we were counting on from you!'

Churchill (left) at the start of the First World War did not provide Lord Kitchener (right) with spare ammunition

The letters give an insight into the testing relationship that existed between the pair. Churchill is said to have 'despised' the army officer, while Kitchener regarded Churchill as 'a bit of an up-start'.

Their correspondence was discovered in the National Archives by military genealogy website Forces War Records, while carrying out research on behalf of one of its members.

Tim Hayhoe, managing director of Forces War Records, said: 'This is a highly-significant document relating to two of the most important figures in the war.

'The letter was written during the very early stages of the war but it shows that the British army was in dire straits at the time and had a lack of resources, particularly ammunition.

'Britain went to war on August 4, 1914 after Germany broke a pact not to invade Belgium.

'We weren't very well prepared at all and sent around 240,000 men to Belgium but it was a token force compared to the Germans who outnumbered the British and Belgians by five to one.

'There was chaos and confusion and shock as the Germans steamed across Belgium and pinned the two forces down in a pocket around Antwerp with the remainder of the BEF bravely fighting a retreat southwards into France.

'That clearly comes across in this fascinating letter as does the sense of urgency.

'Yet here are the head of the army and the head of the navy apparently arguing over their allocation of ammunition, not only that but they seem confused as to who was supplying who.'

Kitchener's face appeared on First World War recruitment posters with the slogan 'Britons: Lord Kitchener Wants You. Join Your Country's Army! God save the King'

Lord Kitchener making his great recruiting speech in 1914 at the Guildhall. Winston Churchill, First Lord of the Admiralty, the civil and political head of the Royal Navy, is seated three to his right

Mr Hayhoe added: 'Kitchener, who regarded Churchill as a bit of an up-start, has written a fairly worded letter and that has been rebuffed by Churchill who is clearly sticking to his guns.

'There is no love lost between the two of them.

'We obviously went on to win the war but people don't often realise how close we came to losing it on occasions and this was one of them.

'The Germans had a massive force and it was up to Britain and Belgium to stop them. If we hadn't stood and fought the Germans in Belgium they would have been in Paris, knocked out the French and then gone for the Russians before they had mobilised.'

In 1916, Churchill returned to the army as a lieutenant colonel of the Royal Scot Fusiliers after the disastrous Gallipoli campaign.

Kitchener was killed in the same year when the war ship taking him to negotiations in Russia was sunk by a German mine.