There are a lot of games that are played in real time and involve strategy before then, and I'll happily call them real time strategy games. But Dune II is the

There are a lot of games that are played in real time and involve strategy before then, and I'll happily call them real time strategy games. But Dune II is the earliest I know of that combined all the key elements of the classic RTS formula - resource collection and management, base building, technological development, etc.