1. e2e4  1... e7e5  2. g1f3  2... g8f6 The Petroff has always been a reputable defense, but lately it's appearing more and more in elite games, having been GM Nepomniachtchi's main weapon in the 2022 Candidates Tournament. 3. f3e5  3... d7d6  4. e5f3  4... f6e4  5. d2d4  5... d6d5  6. f1d3  6... f8d6  7. e1g1  7... e8g8  8. c2c4  8... c7c6  9. f1e1  9... c8f5  10. d1b3  10... d8d7 All this is the latest fashion in opening theory. Here Caruana played the now famous novelty 11.Nh4 and got a great position against Nepomniachtchi in the Candidates Tournament, despite the game ending in a draw. 11. c4c5  11... d6c7  12. b3c2 This move is a theoretical novelty. 12.Nc3 and 12.Nbd2 are more common. The idea is to challenge the e4-knight.