This list of formation types is designed to help beginning Republique players to relate real life Napoleonic formations with those used for game play. The list indicates only very basic averages, and players should remember that real life units varied enormously in both quality and size. In some armies, "green" troops were fully trained and could perform very impressively. In other cases, regular troops who had been allowed to become demoralized put in very poor performances. Unit descriptions include type, average size (number of bases) and average troop grade. The infantry lists also include skirmisher availability and quality. The cavalry lists include a classification of cavalry types. At the beginning of each section is a short description of each army, along with an average ratio of artillery batteries to infantry/cavalry bases. These recommended artillery ratios are purely for reference to help players develop a fair sense of usage.

The Skirmish column describes the number and type of skirmish markers which a unit type is allowed to deploy. A "One" indicates that the entire unit may deploy only one skirmish marker at any one time. "All" indicates that unit type may deploy one skirmish marker per active combat base present.

The Spanish Army of the Napoleonic Wars was nearly destroyed in the early fighting against the French. After this short but sharp period, many battles were fought using militia and armed peasant groups, who showed a singular inability to counter highly trained troops. The result was a nearly unending string of horrendous battles and appalling casualties. These ad-hoc forces did have two huge advantages: They were available in a virtually unlimited supply which could appear anywhere, and they either hated the invaders of their country with a religious intensity, or had an eager hope for loot and profit.

After 1808, regular Spanish Army divisions became less common. More common were various ad-hoc forces formed around remnant army units. More than half of these alternate forces could be composed of militia and armed peasants. Garrison forces in major cities would have a much higher proportion of regular army troops. Spanish regular artillery fights as average, other militia artillery fights as green or militia. The French system of formation change was probably never implemented. Recommended artillery ratios for post-invasion field armies: 1809 = 1 battery per 24 bases. 1811 = 1 battery per 16 bases.