When it comes to gigantic land battles, nothing even comes close to Operation Barbarossa,

the codename for the German invasion of Russia during the Second World War. Having

become master of Europe, Hitler launched a massive surprise attack on his former Soviet

allies that, over the course of a couple of years, would spawn several of history's largest

battles. The action around the Ukranian city of Kharkov, known for its tank factories, was

particularly dramatic, with the city changing hands several times as it was captured and

recaptured again and again.