In a game between top players, the opening moves signify not only the battleground they have embraced, but also the terrain they have avoided. In his prime, Garry Kasparov’s opponents would often duck the most critical choices, fearing the champion’s formidable advantage in home analysis of complex positions. But those who yielded an inch at the outset faced an uphill struggle of a different sort, and Kasparov won countless games from that psychological vantage point.