It's a scenario that's often played out in books, movies and other forms of contempary culture - good vs evil in one epic, almighty clash.
And now, right before our eyes, it's playing out in real life, as coalition forces of Iraqi and Kurdish soldiers push towards reclaiming Mosul from the clutches of the Islamic State.
These are circumstances not unlike the Second World War. There are similarities to the seige of Leningrad (St. Petersburg), when the Germans launched an all-out offensive to take the city which lasted from September 1941 to January 1944 in one of the longest and most destructive sieges in modern history.
One could also draw parallels with the other turning points littered throughout modern military history. The Battle of Waterloo in 1815, when Napoleon's troops were dragged into one final, decisive battle and battered into submission; the Second Battle of the Marne in 1918, when the Allies repelled a furious German assault and began the advance which won them the war; or even Sherman's march to the sea during the American civil war, when the American general William Tecumseh Sherman ransacked the heartland of the Confederacy and drained its people's will to fight.
But perhaps the closes parallel is with D-Day, when the Allies plunged the knife into a flagging enemy and took control of the war. Just like the Mosul offensive for Isis, D-Day came at a time when the balance of the war had begun to tilt away from the Nazis - after early advances, they had lost huge tracts of land, and the aforementioned siege of Leningrad had ended in failure. The time was ripe for a turning of the tide, just as it is now in Iraq.
D-Day wasn't a surprise attack - the Germans didn't know exactly where the Allies were going to strike, but they knew a strike was going to happen. Rather it was a huge frontal assault which held nothing back, its lack of subtlety tempered by an iron collective will to succeed. Those currently attacking Mosul will hope to call on the same strength of resolve.
D-Day began an inexorable advance, with Allied troops liberating key cities like Paris and Rome in the process. Before D-Day, the war was still in the balance. After D-Day, there was only ever going to be one outcome.
Mosul has been under the control of Isis since the group expanded its territory to 40% of Iraq in a lightning offensive in 2014. For two years, Iraqi and Kurdish forces backed by US airstrikes have been fighting to reclaim ground from the group, which has raised its profile through a series of high-profile terror attacks on mainland Europe and Africa.
The shootings on the Charlie Hebdo magazine in January 2015, the gunman on the beach in Tunisia in June 2015, the co-ordinated attacks in Paris in November 2015, numerous bombings in Turkey, the bombings in Brussels, the truck attack in Nice - these incidents have kept Isis in the headlines, kept up their campaign of terror.
But now, it seems, the group is losing control of its heartland. Around 30% of its territory has been ceded. Attacks on foreign cities are all well and good, but the group is beginning to be pummelled on its home turf, and the dream of establishing a Caliphate - just like Hitler's dream of a thousand-year Reich - appears to be crumbling to dust.
For Isis, Mosul was the city they took which allowed them to establish their caliphate. As well as being their bastion, their strategic nucleus, it has come to assume emblematic and spiritual significance, the beating black heart of the Islamist cult.
As long as Isis holds Mosul, the recent loses aren't insurmountable. But if it loses Mosul, the end game could begin in earnest, because the city would be used as a staging point for an invasion of Raqqa, the main city of the caliphate, which already faces trouble from insurrections within it.
That's not to say it will be easy. In fact the strategic significance of Mosul will likely make the battle even harder for the Allies to win - just as the strategic importance of the Omaha beachhead made the Germans fight like tigers to defend it on June 6th 1944.
The caliphate is going to fight tooth and nail in a nihilistic fashion to defend its territory, using their army of suicide bombers and armor-plated truck bombs to maximum effect. Indeed, reports are already emerging of suicide blasts killing Iraqi troops. At least, the explosive devices left by the Nazis on the Normandy beaches didn't move; in Mosul they present a constant, moving danger.
Whatever the outcome, it is this battle which will go down in history. If Isis are defeated, it will be remembered as one of the crucial battles of our time, like the battles of Waterloo and the Marne, the Siege of Leningrad and of course, D-Day.