What makes a great fictional army? Is it the cool uniforms, the powerful weapons, or the slick spaceships?

Video games have always had a fascination with war, and because of that they have given birth to many memorable armies. The best ones are usually aesthetically pleasing, but their greatness always lies in their complex motivations and beliefs.

Here are the greatest armies in gaming.

10. Imperial Guard
(Warhammer 40K)

There are billions of soldiers in the Imperial Guard, and all of them will likely die in service to the Imperium. While the Space Marines get the most attention (and have even been given their own game), the Imperial Guard does most of the heavy lifting in combat. They are not genetically enhanced like their Space Marine brothers, nor do they have the strength and endurance of the Orks. The Guardsmen overwhelm their enemies with sheer numbers, artillery, and armored tanks. These men and women willingly fight physically superior enemies with the knowledge that they probably won't survive the battle.

9. Aliens
(XCOM: Enemy Unknown)

In XCOM: Enemy Unknown, the purpose of the aliens’ attacks is mysterious for much of the game. The world’s best soldiers at XCOM must locate and exterminate the extraterrestrials. The technologically advanced aliens press XCOM to improve their own technology in order to survive. The organization even imbues some of its soldiers with psychic abilities.

At the end of the game, it becomes clear that the alien army’s motivations are more complicated than XCOM first thinks. The aliens believe that their actions are for the greater good. This makes them more complex and interesting than aliens that just want to kill all humans.

8. 33rd Infantry
(Spec Ops: The Line)

Modern military games tend to portray the American military as the good guys, but Spec Ops: The Line blurs the line between good and evil. The 33rd Infantry of the U.S. Army, led by Colonel John Konrad, is sent into Dubai to help evacuate citizens before a sand storm hits the city. However, the storm arrives before the evacuation is complete and they are ordered to leave. 

The 33rd ignores the orders, choosing to stay to help those left behind. They’re willing to face treason charges in order to do the right thing. But, months later, when they fail to evacuate a group of citizens past the massive storm wall that permanently surrounds the city, thousands die as a result and the remaining population becomes unruly. Refugees begin to rebel against their “protectors”, forcing the 33rd to declare martial law to maintain order. Soon, they are forced to fight the very people they were trying to protect in the beginning. The 33rd Infantry demonstrates the cold reality of military occupation. Even with the best intentions, occupying forces will always be seen as a villain by the occupied.

7. Combine
(Half-Life series)

Little is known about these, which makes them more terrifying. What we do know is that the Combine isn’t content with ruling their own universe – they want to control other universes as well. By the time they take over Earth – in an invasion that only takes seven hours – their armies have already conquered numerous other dimensions. Walking through City 17 for the first time is enough to show how completely the Combine has dominated humans. They even turn some of the population into their own soldiers to control the rest. 

Unlike most alien armies, there is no hope for a human victory in a war with the Combine forces. They are so large and technically advanced that the only way that Gordon Freeman can save Earth is by closing the super-portal that they use to traverse dimensions. Of all the enemies on this list, the Combine are the most daunting.

6. Master’s Army

In Fallout, the U.S. and China enter a nuclear war that nearly wipes out humanity and leaves behind a lawless wasteland. Decades later, Dr. Richard Grey, a vault dweller, stumbles upon a facility that the U.S. government used to create chemicals to inoculate people from diseases and radiation. The chemical, called Forced Evolutionary Virus (FEV), also has the side effect of turning humans into disfigured super mutants. 

Now calling himself the Master, Grey realizes that super mutants, with their improved strength, endurance, lifespan, and immunities, are the next step in the evolutionary process. He reasons that such perfect beings would never start another nuclear war. The Master kidnaps and converts unwilling test subjects to build an army of super mutants. He then uses the subjects to collect even more humans. Like a few other armies on this list, the Master’s Army stands out because it attempts to destroy humanity in order to build something better. Unfortunately, the Master’s plan has a crucial flaw: Mutants are sterile and cannot reproduce. Whoops.

[Next up: The top five entries in the list, including armies from StarCraft and Halo]