What does Siege Discipline do in AoE3?

Elite Ram: population −1; Light Cannon: population −1; Elite Mantlet: population −1. The game says: "All Siege Workshop troops cost less population."

Home City card

Siege Discipline

Siege Discipline (tech ID HCXPSiegeDiscipline) is a Home City card in AoE3: Definitive Edition 100.19.18309, in the decks of 1 civilization, sent from the Fortress Age. Effect: Elite Ram: population −1; Light Cannon: population −1; Elite Mantlet: population −1.

Quick answers (3)

Which civilizations have the Siege Discipline card?: Haudenosaunee.
What does Siege Discipline do in AoE3?: Elite Ram: population −1; Light Cannon: population −1; Elite Mantlet: population −1. The game says: "All Siege Workshop troops cost less population."
What is the tech ID of Siege Discipline?: HCXPSiegeDiscipline.

All Siege Workshop troops cost less population.

What it does

Elite Ram: population −1
Light Cannon: population −1
Elite Mantlet: population −1

Cost: 1
Sent from: III
Times it can be sent: 1
Game ID: HCXPSiegeDiscipline

In these decks

HaudenosauneeIII×1

Source: techtreey.xml and the Home City files, AoE3: DE 100.19.18309 (build 25040513).