Stringent supply restrictions – units out of supply may not be activated for movement or combat, and are permanently eliminated if supply is not restored – force players to try to keep continuous lines. Multinational attacks are subject to the restriction that one stack must contain units of each attacking nationality, so a major Allied offensive on the Western Front – to achieve greater attacking strength and to spread the casualties – might require 3 or 4 operations points to activate. The Central Powers are subject to the same restrictions, but have some cards (Sud Army and 11th Army) which allow greater German-Austro-Hungarian co-operation.