He entered Russia by crossing the frozen Vistula River at the head of 40,000 men, approximately half of them cavalry. This tactic was characteristic of his military style, which relied on moving armies with great speed over unexpected terrain. As a consequence of this rapid initiation of the campaign, Charles nearly gave battle with Peter the Great just one month into the campaign, reaching Hrodna, now in Belarus, a mere two hours after Russian forces had abandoned it.