BigDubUSA I was responding to Americanpatriots post not commenting on the war in Iraq, which btw I have always and still support. Nor did I say that Americans said the war would be over by Christmas. It was the Europeans
$1:
Look at the plain numbers and the talent....There is no question who would win once the british are gone! Its over we all know it would be over!
Some more examples of wars not going to plan.
Greco-Persian Wars 499 BC-479 BC:
The Persian Empire sends a massive army to crush the city states of Greece. In every engagement the Persians had massive numeracal superiority (though the Greeks fielded better trained military forces) and smart money said they would crush the Greeks. After such battles as Marathon, Platea and Salamis as well as the Spartan king Leonidas stand at Thermopylae the Persians where sent home crying.
March of the 10,000 401 BC
A force of Greek mercenaries accompanies a Persian prince attempting to steal the throne from his brother. After marching from the coast of what is now Turkey to what is now Central Iraq, they met the Persian army. Though they mercenaries where sucessful there employer was killed in the battle (Cunaxa). The Greeks under Xenophon had to march from Central Iraq, north through Kurdistan, along the coast of the Black Sea to Turkey and cross to Greece facing the Persian army and hostile tribes men almost every step of the way. It was thought to be a suicide run, instead the Greeks managed to get home after lot's of marching and hard fighting.
Alexander the Great 336 BC-323 BC
No need to explain this one I think. Who in there right mind would have thought Alexander and his tiny army could have managed to constantly smash the Persian armies and overrun the entire empire? But they did.
Punic Wars 264 BC-241 BC,218 BC-201 BC, 149 BC- 146 BC
The conflicts between Republican Rome and the Carthagian Empire. The first war started over a dispute in Sicily. Rome at the time was a land power and had little experiance in naval warfare well the Carthagians where masters at it. However after initial reversals Rome managed to build a navy and defeat Carthage in an unexpected reversal, imposing humilating terms on Carthage. The 2nd war was fueled by Carthage's desire for revenge. It was thought the Alps couldn't be crossed, but Hannibal did it and surprised Rome inflicting defeat after defeat on the Republic. Rome ended up fighting in Italy, Spain, Macedonia, against Carthage and her allies. Hannibal even threatned to take Rome at one point. It looked as if Rome was done for the count, but she rallied and defeated Carthage's Macedonian allies, killed Hannibals brother and fellow general Hamiclar in battle, conquer Carthages holdings in Spain and mount an offensive at the city of Carthage itself, destroying the Carthagian empire leaving her little more then a city state. About 50 years latter the Romans returned to finish the job and wipe Carthage from the face of the Earth. What was said to have been a simple task took 3 years of hard bloody fighting. The Romans won but it cost them more then they thought.
The Jewish Revolts 66 AD-73 AD, 133-135
In 66 AD Rome was in control of Judea. Well always having problems with the Jews who refused to submit fully to Roman rule, the storm exploded in 66 AD when the Jews rose against the Romans. Well the Roman's where confident of swiftly crushing the Jews due to there soldiers training and better equipment their fanatical adversaries they faced 8 years of fighting. The Jews would again rise under Shimon bar Kochba in 133 giving the Romans another bloody campaign to deal with.
I'll jump ahead a bit now
War of 1812 1812-1815
The United States declares war on Britain and invades her Canadian colonies. Well almost everyone is confident that the Americans will swiftly overrun the colonies every invasion attempt is repulsed, indeed for a while American territory is occupied and Washington DC raided. However the American navy is remarkably succsessful against the supposedly invincable Royal Navy (granted the Brits where distracted by the French). War ends where it starts.
I've already mentioned the First World War. In addition it and the Second World War have way to many examples to list (and I'm getting tired of typing

) of the battles and what not no occuring or turning out as expected. In addition everyone thought a Jewish state would be wiped out by the Arabs in 1948, it wasn't. In 1967 no one could have predicted in 6 days Israel would wipe the floor with the Egyptian, Jordainian and Syrian armies. There is tons more examples if you look for them.
Many things factor into why a war is won or lost. Training, Numbers and Equipment are factors. So is motivation, terrain and home turf advantage, leadership, weather, Acts of God and other untangibles also refered to as Factor X, politcal will and the will of the people are all factors. There are more. Don't be to quick to declare victory, it could bite you in the ass.