C42 – 1. e4 e5 2. Nf3 Nf6 – Petrov’s Defense xx

├── C42 - 1. e4 e5 2. Nf3 Nf6 3. d3 - Petrov's Defense (1)
├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nc4 - Petrov's Defense: Paulsen Attack (5)
├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nd3 (2)
├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. Bd3 - Petrov's Defense: Millennium Attack (7)
├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d3 - Petrov's Defense: French Attack (4)
├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Bd6 - Petrov's Defense: Classical Attack, Marshall Variation (16)
│   ├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Bd6 7. O-O O-O 8. c4 c6 9. c5 - Petrov's Defense: Classical Attack, Marshall Variation (1)
│   ├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Bd6 7. O-O O-O 8. c4 c6 9. Nc3 - Petrov's Defense: Classical Attack, Marshall Variation (3)
│   ├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Bd6 7. O-O O-O 8. c4 c6 9. Qc2 - Petrov's Defense: Classical Attack, Marshall Variation (2)
│   ├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Bd6 7. O-O O-O 8. c4 c6 9. Re1 - Petrov's Defense: Classical Attack, Marshall Variation (8)
│   ├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Bd6 7. O-O O-O 8. Re1 Bf5 9. c4 - Petrov's Defense: Classical Attack, Marshall Variation (1)
│   └── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Bd6 7. O-O O-O 8. Re1 Bf5 9. Nc3 - Petrov's Defense: Classical Attack, Marshall Variation (1)
├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Be7 - Petrov's Defense: Classical Attack (12)
│   ├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Be7 7. O-O Bf5 - Petrov's Defense: Classical Attack (5)
│   └── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Be7 7. O-O Nc6 - Petrov's Defense: Classical Attack (7)
├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Bf5 - Petrov's Defense: Classical Attack (5)
├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Nc6 - Petrov's Defense: Classical Attack, Mason-Showalter Variation (5)
├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. Nc3 - Petrov's Defense: Nimzowitsch Attack (13)
│   ├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. Nc3 Nf6 6. d4 Be7 7. Bf4 O-O - Petrov's Defense: Nimzowitsch Attack (1)
│   ├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. Nc3 Nf6 6. d4 Be7 7. h3 O-O - Petrov's Defense: Nimzowitsch Attack (1)
│   ├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. Nc3 Nxc3 6. dxc3 Be7 7. Be3 Nc6 - Petrov's Defense: Nimzowitsch Attack (2)
│   ├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. Nc3 Nxc3 6. dxc3 Be7 7. Be3 Nd7 - Petrov's Defense: Nimzowitsch Attack (3)
│   ├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. Nc3 Nxc3 6. dxc3 Be7 7. Be3 O-O - Petrov's Defense: Nimzowitsch Attack (3)
│   ├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. Nc3 Nxc3 6. dxc3 Be7 7. Bf4 Nc6 - Petrov's Defense: Nimzowitsch Attack (2)
│   └── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. Nc3 Nxc3 6. dxc3 Be7 7. Bf4 O-O - Petrov's Defense: Nimzowitsch Attack (1)
├── C42 - 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. Qe2 (2)
└── C42 - 1. e4 e5 2. Nf3 Nf6 3....... - Petrov's Defense (1)