Imagine Country A's fighting force is based on the Roman Legions. Standard soldier carry a javelin and a melee weapon. (These can vary but are one-handed.) They also carry a large shield. As part of state-required law, citizens practice battle skills at least one day a week. (Similar to England's long bow practice.)
Country B styles its army off the tercio. Pikemen keep enemies at bay and short bow archers behind the pikemen shoot at enemy soldiers. There is no required civilian training like Country A, but of course the soldiers are trained.
So how would these armies fare when fighting each other in different conditions? (Examples: Open plains. B defends against A in mountains and vice versa.) These countries are also supposed to have been fighting each other on and off for a long time so adjustments to strategy are realistic.