Sierra

Joint Task Force is a PC real-time tactics game where players command military forces in combat situations based on modern day conflicts.

Homeworld 2 is the 2nd game in the Series by Relic & Sierra. The Homeworld series is a Scf-Fi space-based RTS. It was (and largely still is) unique in it's integration of easy-to-navigate 3D battles.

Empire Earth is a 2001 real time strategy game for the PC by Sierra

The first fully three-dimensional real-time strategy game. Released in 1999.
Other parts of the series are Homeworld: Cataclysm (2000) and Homeworld 2 (2003).