Seven Hour War
From Halflife2.net Wiki
The Seven Hour War was the battle between Earth's armies and the invading Combine forces, after they started teleporting in endless waves once Earth's location had been discovered thanks to the Resonance Cascade.
The reason for Earth's armies being defeated in an extraordinaryly mere seven hours, was because they had already become weakened due to The Portal Storms, they were forced to ferry all remaining civilians into the cities, where they fortified them. Much manpower, time and resources went into dealing with the threat of The Portal Storms. Another factor was the fact that the Combine forces were being teleported in endless waves from inside the cities themselves, behind their strong defences. They did this by transporting Citadels, like the one seen in City 17, right into the center of the cities where they created their own foundations. The military's weapons, which would have been more like our present day military weapons, would have been no match for the sheer capacity and power of the Combine war machine, who had the resources of at least an entire Universe behind them.
After Earth's armies had been massacred, Earth surrendered to the Combine rule through that of Dr. Breen, who was later positioned in a high place of authority; governing City 17 as its administrator from within its Citadel. The evidence of the Seven Hour War that the player sees, is inside Black Mesa East in Half-Life 2, on a board containing numerous other interesting newspaper clippings.
