Games like The Undead War
Games like The Undead War include Mage and Monsters, FTL: Faster Than Light, 911 Operator, Mechabellum, and Bomber Crew. We matched them by the tags players give The Undead War on Steam (Auto Battler, Perma Death, Roguelike, Strategy, and Simulation): closest matches first, and among equally close ones the better-known games.

Mage and Monsters
Shared: Auto Battler · Perma Death · Strategy

FTL: Faster Than Light
Shared: Roguelike · Strategy · Perma Death

911 Operator
Shared: Strategy · Simulation · Management

Mechabellum
Shared: Auto Battler · Strategy · Wargame

Bomber Crew
Shared: Simulation · Strategy · Management

This War of Mine
Shared: Strategy · Simulation · Choices Matter

Totally Accurate Battle Simulator
Shared: Simulation · Strategy · War

Game Dev Tycoon
Shared: Simulation · Strategy · Management

Mini Motorways
Shared: Strategy · Simulation · Management

Crusader Kings III
Shared: Strategy · Simulation · Management

Teamfight Manager
Shared: Auto Battler · Simulation · Management

Super Fantasy Kingdom
Shared: Auto Battler · Strategy · Roguelike

Total War: WARHAMMER II
Shared: Strategy · Fantasy · War

Plague Inc: Evolved
Shared: Strategy · Simulation · Indie

Backpack Battles
Shared: Auto Battler · Strategy · Roguelike

Wargame: Red Dragon
Shared: Strategy · Wargame · Simulation

The Last Flame
Shared: Auto Battler · Roguelike · Strategy

9 Kings
Shared: Auto Battler · Strategy · Roguelike

Mage and Monsters II
Shared: Auto Battler · Perma Death · Strategy

Eslabong
Shared: Auto Battler · Strategy · Management

Gladiator Guild Manager
Shared: Auto Battler · Strategy · Management

Total War: WARHAMMER III
Shared: Strategy · Fantasy · War

Cities: Skylines
Shared: Simulation · Strategy · Management

Dwarves: Glory, Death and Loot
Shared: Auto Battler · Roguelike · Strategy