[2] In the winter of 928, King Henry the Fowler of Germany organized a military expedition along his eastern frontier against various Slavic fortifications.
[6] On their way to Gana, Henry's army marched along the Plane valley to the Fläming hills, conquering more Slavic forts at Belzig, Mörz, Niemegk and Zahna.
[8] Filling in a 200-meter section of the ditch was necessary for Henry's men to storm the walls, a process that would have required the excavation of 15,000 tons of earth with at least 50,000 man-hours of work.
[11] Once Gana was stormed at the end of the 20-day siege, Henry gave the order for his men to kill all the defenders and enslave the young boys and girls to his milites professional soldiers.
[12] After conquering Gana, Henry marched up the Elbe to accomplish his ultimate campaign aim, the siege of Prague and the subjugation of Duke Wenceslaus I's Duchy of Bohemia.
[12][13] With the help of Duke Arnulf of Bavaria's troops, Henry invaded Bohemia with a total force of 12,000–15,000 professional soldiers and expeditionary militia levies and compelled the surrender of heavily-fortified Prague, concluding a highly successful campaign.