The Traxler Counterattack, also known as the Wilkes-Barre Variation, is a chess opening that begins with the moves: The opening is a variation of the Two Knights Defense[1][2] where White has chosen the offensive line 4.Ng5, immediately attacking the f7-square with the knight and bishop, and Black has replied 4...Bc5, counterattacking the f2-square.

[4] Later it was named after Wilkes-Barre, Pennsylvania by Frank Marshall, who claimed to be first to analyze and publish it, so today 4...Bc5 is known as both the Traxler Variation[4] and (in the United States and the United Kingdom[5] only) the Wilkes-Barre Variation.

The knight is defended by the bishop on c4, and is forking the black queen and rook.

(diagram) will draw out the white king and bring the black queen into play with gain of time.

[10] If White blunders by taking the rook on h8, a common beginner mistake, mate in four follows: 8...Qf4+ 9.Ke2 (9.Kd3 Nb4+ 10.Ke2 Qf2#) Qf2+ 10.Kd3 Nb4+ 11.Kxe4 Qf4#.

[10] This move is preferred by most modern masters, winning a pawn and avoiding the complications that arise after 5.Nxf7 Bxf2+.

White is considered to have a slight edge, but lagging in development due to having to move the bishop and knight multiple times.

[12][13][11][10] The main line continues with 6.Bd5 (also possible are 6.Bb3 and 6.b4), which is often given an exclamation mark by theory books.