An attacker attacking from multiple spaces may attempt a "flank attack". If successful, the attacker attacks first, only after which can the now weakened defender fire back – the opposite is the case if the flank attack fails. This tends to be a key tactic on the more mobile Eastern Front. Players may dig "trenches" under their counters, which besides weakening the attacker, strengthening the defender and making the defender immune from flank attacks, also allow defeated forces to avoid retreat at the cost of extra casualties, thus potentially making a densely packed Western Front as immobile as it was in reality. Certain other forms of terrain (e.g. mountains) also have similar powers to trenches. The map also contains numerous printed fortresses (e.g. Liege, Antwerp, Verdun, Pryzmysl, Riga), which may be destroyed in combat or besieged.