Elite Spear Tactics is a campaign-exclusive technology in Age of Empires IV that can be researched at the Blacksmith in the Imperial Age. The technology increases the attack speed of Spearmen by +12%, and they deal +25 more damage when braced against a cavalry charge. It is available in all four original campaigns, but was removed in all other game modes.
The Mongols can research the improved version of the technology for an additional 450 stone. It further increases the attack speed by 23% (+35% total) and the brace damage by 15 (+40 total).
