WW1 concentrates on the land war in Europe from 1914-18 with the effects of naval conflict abstracted. The first interesting aspect is the Sequence of Play. Dunnigan uses a multi-phase approach which works well in representing the long length of time of one turn. Units can also abstractly move from France to Italy via spending a turn in a transit box. Defenders receive a strength bonus of 1 in rough terrain which covers most of the southern West Front, Italian spine, Balkans and Austro-Russian border, and another bonus of 2 in Winter turns which make up 5 of the 10 turns.
Attackers can advance after combat.
CP supply is traced to cities. OOS units can't attack, defense is halved, and more importantly, can't use CRP to take losses. So if they can't retreat, they are eliminated. Building units cost 5 CRP ea. with the counter mix serving as a design limit. CRP gains or losses are noted on a map track for ea. country.