HALLE (Reuters) - Germany's Philipp Kohlschreiber won the Halle grasscourt tournament on Sunday after countryman Philipp Petzschner retired with a back problem. In the first all-German Halle final since the Wimbledon warm-up event started 19 years ago, the pair slugged it out in an exciting first set before the 27-year-old Petzschner retired, trailing 7-6 2-0. World number 49 Kohlschreiber landed his first singles title since Auckland in 2008. Both players dominated on their service games on the extremely fast Halle grass, making it virtually impossible for the returner to forge any break chances. Fans on the sun-drenched centre court had to wait 11 games to see the first break point when Kohlschreiber fired a stunning return. However, he failed to convert it and the set went to the tiebreak.