Caruana chose the Petroff 2 Nf3 Nf6, which used to be the weapon of choice for players aiming for a half point as Black, was relegated for some years due to the popularity of the Berlin 1 e4 e5 2 Nf3 Nc6 3 Bb5 Nf6, but has returned to favour as the main line Berlin with an early queen swap has been outmoded by 4 d3.

In that game, Carlsen sidestepped the main line of the Berlin Defense with 4 d4, hoping to unsettle Karjakin. That did not work, and chances were equal for most of the game.

8.Qd2 is the old main line of the Poisoned Pawn from the days of Fischer and Kasparov.

Adams, the No1 seed in the Isle of Man, has always favoured 3 Nd2 against the French and, when his Polish opponent, below, followed a main line, Adams was very willing to go along.

March 22 2023, “Tickets now on sale as trial Swanage service finally gets green light”, in RAIL, number 979, page 25:
Gavin Johns, chairman of the Swanage Railway Trust, said: "I would like to thank our stakeholders for their far-sighted investment of £5.5 million to re-connect Swanage and Corfe Castle with the main line, which included £1.8m from the Government's coastal communities fund, so we could restore our 1950s heritage diesel trains for running on the main line."

Main line

Meaning

Noun

Adj