Mine would be the Mongols, started with Genghis Khan and moving into Ogedei Khan.

Not only did the man manage to unite all of the disparate tribes of Mongolia, but went on a conquering spree that resulted in conquering one of the largest land masses in history. He also had Subutai, considered to be one of the greatest generals in human history.

The man also may have some of the most genetics spread in the world: http://blogs.discovermagazine.com/gnxp/2010/08/1-in-200-men-direct-descendants-of-genghis-khan/

In turn, Ogedei conquered Persia and pushed into Europe. Guyuk, next Khan, didn't do much. Mongke Khan, though, was responsible for the sacking of Baghdad and the destroyed the libraries of Islam. In turn, they figure that may have changed world events in that it was the end of the Islamic Golden Age.

If you want an army that is large, strategic, invented new policies when it comes to conquering one's enemies and are outright brutally effective, not to mention potentially world changing, you can't beat the Mongols.

apm and hjs bare fucking handsw

SAFHF

Bingo. It's hard to imagine a bunch of steppe hunters and herders conquering every land and people from Korea to Hungary and Siberia to Persia, but they did it, and in a way that was completely unforeseen by their enemies.

I'm named "Mr Khan" for a reason (that has nothing to do with Star Trek).

I'm going to go with Mongols also considering they had one of the largest land empires. Their tactics such as withdraw (bait the enemy) while turning around and firing off salvos of arrows from their horse archers every once in awhile made it almost impossible to track them down and kill them.

I also like the Vikings during the Middle Ages. They weren't incredibly dominate but they were supreme raiders and opportunist. They also settled in the Normandy area (Rollo), helped establish Russia (Rus Vikings), introduced ideas such as all men are created equal, and helped show Europe that they needed to defend their coast lines/ group up together to better defend themselves. They also had the best boats for the time and helped explore a lot. They deserve all the credit for find Americas by boat (not Christopher Columbus).

The Spartans of course

Depends on what you mean.

If your asking what Military force would kill any other in a deathmatch the clear winner is either the US Navy SEALS or the US Marine Corp.

Even the Mongols with their massive number of units would be absolutly wrecked by a couple small teams of snipers and machine gun fire. But then again thats kinda not a fair comparison

The SAS would wipe the floor with Navy SEALS!

Lol sorry but theres no evidence SAS are better than the SEALs. SEALS handle pretty rediculous missions constantly. While SAS are good they are nowhere near as battle hardned.

Anyways my favorite.......hmm tough to say. Im not a big fan of the Mongols as they created Biological warfare which is a cowards way of fighting. IDK ancient Greece and Rome were both pretty badass

I liked this story....  Basically it worked but then a big storm sank a bunch of the ships because they were too top heavy...  I just remember it from a History Channel episode.

"Instead the Romans pin their hopes on a device which has already featured briefly in Greek naval warfare, but not to much effect. It is designed to give Roman soldiers, trained in the legions, a more stable platform from which to attack.
         
This device is a hinged drawbridge which can be released to crash down when an enemy ship is alongside. On its underside is a metal point, which will pierce the deck of the vessel and hold it fast while the Roman troops storm aboard. The lethal peck from this sharp beak gives the device its familiar name among the crews. It is a 'raven'. And it wins them battles.

The first such victory comes as a major shock to the Carthaginians. They have an advantage of thirty ships over the inexperienced Romans when the fleets meet in 260 BC off Mylae (now Milazzo), a few miles to the west of Messina. But the ravens enable the Romans to destroy fifty Carthaginian ships before the rest flee in panic.
         
The Battle of Actium: 31 BC

Roman warships abandon the raven soon after its first successes against the Carthaginians. The reason is probably their heavy losses in storm conditions. The raven in its upright position may have proved top-heavy."