The Russian invasion of China to drive the Japanese out in WW2, they rolled over the Japanese is they weren't there. they destroyed a Japanese army of some 850.000 men in a couple of weeks

The Battle of the Atlantic, while strictly more of a campaign then a battle, it cost so many lives, Merchantmen and as well as Navy.

in Stalingrad Soviet losses were excessive in spite of the fact that the Germans had few planes, guns, ammo fuel and food and tanks were of little use, mostly owing to extremely stupid Soviet leadership.

A far more interesting battle and very little known is Rzhev. So fierce, deadly and long that both the Nazi and the Soviet propaganda buried it. It was Zhukov's darkest our.

Also in China, a battle so fierce that the Japanese lost all their officers and had to drop by parachute officers to lead the troops.

If fiercest means fighting till most die, read about the origin of the term Pyrrhic victory or check out the Mongol destruction of Bagdad, at that time the most advanced and wealthiest city in the world.

Also the Germans breaking out of the Pocket of Demyansk or holding the pocket or Courland or the Soviets holding the pocket of Oranienbaum. Excellent Generalship and quality fighting on the 3 cases.

Any battle that you are in

I whole heartedly agree with Lee Enfield - the one you’re in is the fiercest.
But for consideration I offer Cameron, Mexico, 1863; Dien Bien Phu, French Indochina, 1954; Teutoburg Forrest, Germany, 9 CE; and Cannae, Italy, 216 BC.
But, truthfully, I think there are far too many to list just one.

Berlin, The 8 month siege of Sevastopol, the most fortified place in history, which required 800 mm guns, the 900 day siege of Leningrad, Tarawa, Guadalcanal, Iwojima, Okinawa, and some great, bloody naval and air battles, besides the battle of the Atlantic, already mentioned: The destruction of the Persian fleet, Actium, Lepanto, the Great Armada, Trafalgar, Midway, the BoB, Truk, Malta, Crete, Operation Bodenplatte, etc,

what a question? MODERN battles To an american,battle of the bulge ,heutgen forest ,saipan ,okinawa guadal canal,Australian, passendale gallipoli,ypres,tobruk, new guinea ,greece, crete and a lot with the British, malaya,British,dunkirk, burma,hong kong, malaya, arnhem Russia leningrad, stalingrad, kursk, sebastopol. ANCIENT the jews losing jerusalem to Nebucanazza and later again to the Persians, The Egyptians against the Hyskos, The greeks at Thermopalae, the ten thousand fighting their way home from Persia led by Xenophon, Alexanders drive thru Persia to India, Romes great battles thru 700 yrs of conquest, Too many to individually class a single one each were important in their day.There was one in the Middle East by Tamerlane a mountain of 100000 skulls was built by his men after one battle.

Ahem, we were at Gallipoli too. i hate it when i watch doco about it and its only about AUSTRALIANS!!!

The little known even in Spain Battle of Teruel.

http://en.wikipedia.org/wiki/Battle_of_Teruel

My grandfather was lucky he was not deployed there.

looks nasty. but i agree with lee enfield (having no experience myself). winter battles are always the worst.