Short blade

The Short Blade is a short, curved blade that is a smaller and a more agile weapon than the longsword. The Short Blade trades power and reach for a faster swing rate. The Animus, in its hints and tips given to the player, recommends the Short Blade for killing off large numbers of enemies.

Assassin's Creed
In Assassin's Creed, the short blade is first available after Altaïr has reached Rank 3. Like the Longsword, Altaïr's Short Blade increases in quality and power with his rank. Altaïr carries the short blade on his back with the handle facing down.

With speed that is faster than the longsword, the short blade can quickly dispatch a large number of weak foes. However, it becomes quite difficult when facing higher ranking enemies, as they have better armor. It seems that the short blade is just a back-up weapon when throwing knives at the enemies. When the enemies get out of the range of the throwing knives, Altaïr can use the short blade to counter a few blows before switching to his more powerful longsword.

While the Short Blade is selected, the player can also use throwing knives by holding down the modifier key and pressing the weapon hand key ( on Playstation 3, X on Xbox 360, Left Mouse Button for PC default layout).

Assassin's Creed II
Ezio can carry a short blade in addition to his longsword. Various short blades can be purchased at blacksmith shops with unique speed, damage and deflection properties. Unlike Altaïr, he won't carry it on his back, but next to his primary weapon. The special attack of most short blades can only be performed from behind, and takes the form of slitting their neck, and stabbing them in the shoulder or the back, which will always result in an instant kill.

It should be interesting to note that the last-tier Short Blade in Assassin's Creed resembles the Sultan's Knife, meaning that in Assassin's Creed it is the most powerful, but in Assassin's Creed II the most powerful Short Blade is the Notched Cinquedea. This is a contrast to the Longsword as a Western Short Blade is the most powerful in-game; but Altaïr's Sword, which is made in the Middle East is the most powerful Longsword in-game.

Trivia

 * The Short Blade is a weapon to be featured in the multiplayer of Assassins Creed: Brotherhood. It will be the primary weapon of the Soldier.