First and foremost are the Seraph, who act as both the backbone of the military and the police force for the Human settlements. While the Seraph are widespread in Kryta, the Ministry Guard -- the protectors of the Human government and nobility -- mainly focus their efforts in the capital of Divinity's Reach. However, watching over the Royal Family is the responsibility of the Shining Blade, an elite force of warriors and spies. The Shining Blade should be familiar to those who fought in Guild Wars' War in Kryta campaign.
Each of these military branches vies for influence and authority over the others, although the Shining Blade tends to be at the top of the pecking order while the Seraph take up position as the whipping boys (and girls). As ArenaNet writes, this causes "a tug-of-war for influence and control" amongst the beleaguered armed forces.
You can read about the clash of politics, position and power between these forces on the ArenaNet blog -- and stay tuned for this coming Monday, when Flameseeker Chronicles will give a colorful commentary on the whole of Human Week.