The Rubinstein System has the incontrovertible practical advantage that in reply to either 3.Nc3 or 3.Nd2 Black can reach the same position by exchanging 3...dxe4 4.Nxe4. He avoids the pawn chain with the cramping white pawn on e5, but in return accepts a disadvantage in space. We already know 3...dxe4 from the Caro-Kann with 3.Nc3/d2, but there is the important difference that in the Rubinstein Variation the e6-pawn shuts in the Bc8. For that reason this bishop is brought into play on the a8-h1 diagonal, either by ...b6, ...Bb7 or via the route d7-c6. A slight advantage for Black is that, compared to the Caro-Kann, he can play the important advance...c5 in a single move.
Akiba Rubinstein often played this system at the start of the 20th century, sometimes also with the insertion of the moves 3...Nf6 4.Bg5 dxe4, a move order nowadays called the Burn Variation. The rise of the Winawer Variation (3.Nc3 Bb4) pushed the Rubinstein into the background for a long time, but it has suddenly become very popular in the games of top players since about 1990, above all on account of its solidity. Thus, for example, the move order 4.Nxe4 Bd7 (intending ...Bc6 and later ...Bxf3) is known as the Fort-Knox Variation.