In the Middle Ages, marches were any type of borderland between realms, or a neutral zone under joint control of two states.
Marches served a political purpose, such as providing warning of military incursions, or regulating cross-border trade.
At the beginning of his rule as king of Germany, Otto I tried to reorganize his realm to prepare an expansion to the East.
In the case of Gero, Otto I, now emperor, decided the division of his territories, greatly expanded since 937.
In 861, Charles the Bald, king of France, created two marches to protect his realm from warriors coming from Brittany and Normandy.