* Kohima was turning point in WW2
* D-Day, Waterloo defeated in contest
By Angus MacSwan
LONDON, April 21 (Reuters) - The Battle of Imphal/Kohima, when British troops fighting in horrendous jungle conditions turned the tide against the Japanese army in World War II, has been chosen as Britain's greatest battle.
Kohima was picked over the more celebrated battles of D-Day and Waterloo in a contest organised by the National Army Museum.
Rorke's Drift in the 1879 Zulu War and the Battle of Aliwal in the Anglo-Sikh War in Punjab in 1846 brought up the rear.
"Great things were at stake in a war with the toughest enemy any British army has had to fight," historian Robert Lyman said, making the case for Kohima in a debate at the museum.
If Lieutenant General William Slim's army of British, Indian, Gurkha and African troops had lost, the consequences for the allied cause would have been catastrophic, he said.
The contest's criteria included a battle's political and historical impact, the challenges the troops faced, and the strategy and tactics employed.
Waterloo had topped an online poll which produced a list of 20 land battles fought since the English Civil War. The top five were debated on Saturday before going to an audience vote.
The winner was something of a surprise given the enduring prominence of Waterloo and D-Day/Normandy in Britain. Indeed, the troops who fought in India and Burma in World War II called themselves "The Forgotten Army".
The Battle of Imphal/Kohima took place in 1944 in Nagaland when Japanese troops poured over the Burmese border to strike at India. Fought over a vast area of jungle and mountain, it was marked by vicious hand-to-hand fighting.
The successful British defence meant they were then able to push into Burma and roll back the Japanese from mainland Asia.
"The victory was of a profound significance because it demonstrated categorically to the Japanese that they were not invincible. This was to be very important in preparing the entire Japanese nation to accept defeat," Lyman said.
He suggested that one reason the battle is relatively unfeted was because Britain itself played it down due to U.S. President Franklin Roosevelt's opposition to empire.
In fact, Lyman said: "This was the last real battle of British Empire and the first battle of the new India."
The Indian troops "weren't fighting for the British or the Raj but for a newly emerging and independent India and against the totalitarianism of Japan."
He ranked it with Midway, El Alamein and Stalingrad as the main turning point battles of World War II.
His adversary in debate, former Parachute Regiment Colonel Stuart Tootal, argued a strong case for the D-Day landings and subsequent Battle for Normandy against Hitler's Germany in 1944.
Although popular culture, including such movies as "Saving Private Ryan", has highlighted the American role and relegated the British to supporting cast, the operation was under the command of Britain's Field Marshal Bernard Montgomery.
His planning skills and ability to keep the Germans guessing was crucial to its success. The capture of Caen by British and Canadian troops allowed the Americans to break out, Tootal said.
The victory decided the outcome of World War II, including denying the Russians total control of Berlin. It's sheer scale and the risk involved made it Britain's greatest battle, said Tootal, a veteran of Iraq and Afghanistan .
"What would have happened if it had failed? The war would have gone on for two or three more years, killing on a mass scale would have continued. And what would have happened to the Jews? The Nazis would have completed the Holocaust."
The Duke of Wellington's victory over Napoleon's French army at Waterloo in 1815 had gone into the final as favourite but was unseated.
Historian Iain Gale said its consequences were immense for Britain and it has "permeated our nation and it's conscience".
Wellington was a brilliant commander, able to read a battle and adapt as it unfolded. Gale lauded the courage of the British soldiers formed up in squares to hold off the Frecnh cavalry.
But he acknowledged a certain amount of luck was involved and the arrival of General Blucher's Prussian forces at the height of the battle was crucial.
Waterloo ended decades of conflict with the French across the globe and Napoleon's attempts to dominate Europe.
"It prepared the way for the British Empire and the modern world as we know it," Gale said.
Rorke's Drift, when 150 British soldiers fought off 4,000 Zulu warriors, has a cherished place in British popular lore. But it lost out in the contest, possibly because despite the heroism, it was of little ultimate consequence.
"No great general, no great strategy, just British soldiers, unready for combat, fighting against overwhelming odds, with no hope of relief," debater Craig Appleton said.
(Reporting by Angus MacSwan; Editing by Andrew Heavens)