Spring 1944!

Set a generation before the events of the original Warcraft began, Warcraft II is a real-time strategy game by Blizzard Entertainment. Cunning, sinister, and seemingly unstoppable, the demonic Burning Legion prepare to launch their long-awaited assault on the mortal world. Survival is a matter of strategy, as the Reign of Chaos begins…

OpenRA is an open-source reimplementation of Westwood’s Command & Conquer: Red Alert game engine, updated to use the hardware acceleration of modern video cards using OpenGL.

Warzone 2100 is a real-time strategy game, originally developed by Pumpkin Studios and published by Eidos Interactive on the Sony PlayStation console, now developed by the Warzone 2100 Project. Compared to other real-time strategy games, it has a greater focus on artillery, radar, and counter-battery technologies, more frequent in-game cinematic updates as game play progresses, a massive research tree, as well as a vehicle design system.

Widelands is a free, open source real-time strategy game with singleplayer campaigns and a multiplayer mode. The game was inspired by Settlers II™ (© Bluebyte) but has significantly more variety and depth to it. Still, it is easy to get started through playable tutorials.

Age of Mythology is based on building towns, gathering resources, creating armies, and ultimately destroying enemy units and buildings. In this way, players are able to defeat and conquer rival towns and civilizations. Players advance their tribe through four "Ages": starting in the Archaic Age, the player may upgrade to the Classical Age, the Heroic Age, and finally, the Mythic Age. Each upgrade to a higher Age unlocks new units and technologies for the player, which strengthens their settlement. »

Globulation 2 is an innovative Real-Time Strategy (RTS) game which reduces micro-management by automatically assigning tasks to units.

Free (as in freedom) open-source RTS http://alternativeto.net/software/age-of-empires-iii/ engine. Written from scratch in C++14 and Python, using OpenGL + GLSL.