Oh, you mean a single-player game with a campaign that carries forward your status from mission to mission instead of giving you new starting conditions for each new map or level.
From Good Old Games / gog.com, these squad-level, turn-based, tactical games fit the bill (but are not RTS)
- Fallout Tactics
- Jagged Alliance 2
Pretty much every PC RPG has your party carrying forward its gains from dungeon / quest to quest.
Old school 2D isometric, also at GoG.com
- Baldur's Gate 1 & 2
- Fallout 1 & 2
- Planescape: Torment
3D :
- Star Wars Knights of the Old Republic I & II
- Vampire the Masquerade: Bloodlines
- Neverwinter Nights 1 & 2
- Morrowind & Oblivion
- Fallout 3 & New Vegas
- Mass Effect 1 & 2
- Dragon Age: Origins