Stanley Variation, Three Knights Variation

The Three Knights Variation of the Stanley Variation arises after 1. e4 e5 2. Nc3 Nc6 3. Bc4 Nf6. It can also be reached from the Stanley move order 2...Nf6 3. Bc4 Nc6, or from the Max Lange Defense, 2...Nc6, when Black adds ...Nf6 after 3. Bc4. Instead of contesting the c4-bishop with ...Bc5 or pinning with ...Bb4, Black develops the king's knight at once and attacks e4, which is defended only by the c3-knight. That leaves White to decide how to deal with the pressure on e4 before going on with development.

The most common answer by a wide margin is 4. d3, the Berlin-Vienna Hybrid. Bishop's Opening move orders such as 2. Bc4 Nf6 3. d3 Nc6 4. Nc3 reach it as well. The pawn on d3 secures e4 and opens the diagonal for the c1-bishop. Because the g1-knight has not yet gone to f3, White keeps the f4 advance in reserve. Black has three main replies. 4...Na5 hunts the exposed bishop on c4, while 4...Bc5 and 4...Bb4 develop the remaining minor pieces. Against 4...Na5, White can play 5. Nge2, which unbalances the position and still leaves the f-pawn free to advance. The engine also rates 4. Bb3 highly. That retreat moves the bishop before ...Na5 can hit it.

The second most popular move, 4. Nf3, transposes to the Italian Variation of the Four Knights Game. It gives up the plan of f4, and in the sample Black scores nearly as well as White after it. The rarer 4. f4 invites the fork trick 4...Nxe4, and 5. Nf3 then gives the Bronstein Gambit.

The engine rates the position as roughly balanced. In the Lichess sample White scores slightly better than Black, and draws are rare. The pairing of Nc3 with Bc4 is sometimes criticized as poorly coordinated, chiefly because the bishop is easy to attack. Most players therefore choose the solid 4. d3 structure, and the game becomes a maneuvering struggle in which the f4 break remains White's main dynamic resource.