Ultrahard Steel

No cannon or musket wins the war against the Titans; the killing is done up close with swords of ultrahard steel. These single-edged blades attach to the vertical maneuvering equipment and represent the only hand-carried weapons capable of cutting Titan flesh. Artillery can wound a giant but aims too slowly, and firearms manage little beyond bursting a Titan's eyes, so the blade remains the decisive tool, wielded in pairs to carve out the nape with precision. Soldiers can also target tendons, fingers, or eyes to cripple a Titan mid-fight, and the metal is light enough that carrying a full rack of spares barely slows anyone down.

The steel comes from one place only: the forges of the production cities, where it is smelted and shaped into blade stock, with no other site able to manufacture it. The recipe blends iron bamboo with rare metals, trading raw mass for a combination of hardness and lightness.

That hardness has a price in brittleness. Edges dull with repeated cuts and worn blades eventually snap, which is why the killing stroke uses two swords at once, since a lone blade risks failure or interruption before the nape comes free. Striking hardened surfaces is worse still; the crystal skin of the Female Titan or the plating of the Armored Titan shatters blades outright. Soldiers compensate by racking multiple replacements on their gear for quick swaps mid-battle. The segmented look of the blades recalls a box-cutter, and their brittleness alongside their edge retention suggests a very high carbon or high chromium composition.

Every branch of the Military fights with these swords, making them the standard sidearm of humanity's war effort. Levi Ackerman pushes the weapon beyond its design, occasionally hurling blades into Titans from range like oversized tomahawks, and proving their lethality against people when he cuts down a pursuer while escaping Kenny Ackerman, the momentum of his maneuvering gear lending force to the strike. The "flesh paring" description applied to the swords hints at a shallow edge angle of roughly fifteen to twenty degrees.