After Anatoly Karpov came Garry Kasparov, the 13th world champion. Kasparov took opening preparation to possibly the most extreme level of any champions before or since. His deep explorations, with the help of a team of grandmasters and -- a new phenomenon at the time -- computers, were a consequence of the much higher level of professionalism of chess.

Novelties were prepared deep into the middlegame, powerful schemes were prepared at home in critical opening variations, and sharp lines were analyzed in great detail.

The backbone of Kasparov's repertoire as Black was the Najdof Sicilian and the King's Indian, although he frequently used other openings, especially in his matches with Karpov, where more solidity was required.

As White, Kasparov tirelessly sought sharp and aggressive but sound approaches after both 1.d4 and 1.e4. In his matches with Karpov, there were great debates with Kasparov playing White in the Zaitsev variation of the Spanish. But at some point, Kasparov introduced what was at first a surprise weapon, from the 19th century: the Scotch Opening.

The Scotch is a perfectly natural way to play, of course, with White quickly piercing the center and gaining space, just as he does in the Open Sicilian. But for much of the 20th century it was neglected, with only a handful of master-level outings each year. It might have looked, in those times, like yet another ancient opening where the tension is released too quickly to give a full game of chess.

When it was played, the players were probably, for the most part, thinking over the board within a few moves into the game.

Kasparov brought science to the Scotch, in particular making deep investigations into the unusual positions resulting after 4...Nf6 5.Nxc6 bxc6 6.e5 Qe7 7.Qe2 Nd5 8.c4

After only eight moves an extremely colorful position has arisen. White has gained a serious space advantage, both queens are awkwardly placed, the black knight is being kicked around, and the white position is in serious danger of being over-extended. The fate of the e5-pawn is absolutely critical to the outcome. Will White keep this pawn and stifle Black? Or will the pawn fall and the white king come under attack? Or -- as is often the case -- will White be able to effectively sacrifice this pawn?

The subsequent play from this position contains a bewildering number of possibilities. To start, Black can play 8...Ba6 or 8...Nb6. Later, both players can castle on either side of the board -- often Black castles queenside to step up the central pressure, and White targets the black king there. All four bishops can be either fianchettoed or developed otherwise. Black may play ...g6 or ...g5 at any point, White can choose to play f2-f4 or not, counterattacks such as ...d6 or ...d5 are always on the agenda, ...a5-a4 (when White has played b3), and there are also tactics such as ...Qb4+ or ...Qh4 at various moments.

In short, there are a huge number of ways this position can be played in the next five moves, yet unlike most positions with large numbers of possibilities, here the play is not calm and based on general considerations, but rather practically every line is sharp and concrete.

This is not like the Spanish, where -- while there are certainly sharp variations -- one can generally make reasonable moves by following basic principles and common sense. Here only by deep preparation can a player feel that he is not riding on the winds of chance.

Thus a player with a high degree of professionalism and work ethic, and gifted by a wonderful memory, such as Kasparov, excels in this variation. Indeed, his record with the Scotch was simply phenomenal: +13 =8 with no losses! And this is against opposition of the highest level.

This, and the fact that Kasparov was almost single-handedly responsible for re-introducing this 19th-century weapon, is why I have chosen the Scotch for this article, despite Kasparov not having played a really huge number of games with it.

Kasparov first produced the Scotch in the 14th game of his last (1990) world championship match with Karpov. This game shows a very common and important theme of the above position: if Black attacks e5 in straightforward fashion, White can simply sacrifice the pawn to keep the e-file closed and turn his attention elsewhere, specifically the Black's queenside castled king.

Kasparov did not win that game, but in his next game as White he repeated the Scotch, and this time he won.

Later, the two champions met at the Tilburg 1991, and Kasparov again used the Scotch. This time Karpov used a more modest method of counterattack: ...g6, intending ...Bg7 and ...0-0. Kasparov adopted his innovation, the very sharp 10.f4. The game immediately exploded into tactics involving a series of desperadoes, which eventually resulted in White's extra piece. Smoothly Kasparov converted the win.

Concerning the variation with 8...Nb6 (instead of 8...Ba6), Kasparov introduced an important concept against Michael Adams, and then improved on his own play a year later against Jan Timman, thus staying ahead not only of his opponents but also a legion of commentators and theoreticians!

This game against Timman shows the depth of his explorations, which probably extended deep into the endgame, and provides not only "opening" theory but also an extremely instructive example of artistic technique.

In the same vein, we see his 2000 game against Etienne Bacrot, wherein a sharp and theoretical opening leads to a thematic endgame. Kasparov then provides a beautiful demonstration of strategic control. The game is a joy to play over:

We can now turn our attention to the main alternative, the much more sedate 4...Bc5. Kasparov initially used the most common move 5.Be3 -- for example here is his nice win against his future challenger for the world championship:

But soon he turned to the less-common but also more scientific move 5.Nxc6. Here White is counting on his kingside majority of pawns, and often is willing to go into an ending where Black receives a couple sets of doubled pawns. Here is his well-known win against Arthur Yusupov, where Kasparov grabbed a pawn and came out on top, although matters were not so clear:

All in all, the Scotch was one of the openings that Kasparov injected with his creativity and his constant striving for perfection. This one was even more dramatic since (unlike, for example, the King's Indian) the Scotch had very little history of being played by top modern masters.

What was once a relatively obscure opening mostly played by masters who were looking to avoid modern theory -- and which frequently led to arid positions, such as the one after 4...Nf6 5.Nc3 Bb4 -- became fleshed out into this theoretical maze, full of wild complications and unusual ideas.

For those who might be inspired to take up the Scotch (and, with the good reputation of the Berlin Defense against the Spanish, it is about time) it might seem intimidating. But remember that you have no better guide than the games of Kasparov to learn the essentials.