While Napoleon had assessed that the Coalition forces in and around Brussels on the borders of north-east France posed the greatest threat, because Tolly's Russian army of 150,000 were still not in the theatre, Spain was slow to mobilise, Prince Schwarzenberg's Austrian army of 210,000 were slow to cross the Rhine, and another Austrian force menacing the south-eastern frontier of France was still not a direct threat, Napoleon still had to place some badly needed forces in positions where they could defend France against other Coalition forces whatever the outcome of the Waterloo campaign.
Kuigi Napoleon oli otsustanud, et koalitsiooni väed Brüsselis ja selle ümber Prantsusmaa kirdepiiril kujutavad endast suurimat ohtu, kuna de Tolly 150 000-meheline Vene armee ei olnud veel teatris, Hispaania mobiliseerus aeglaselt, vürst Schwarzenbergi 210 000-meheline Austria armee oli aeglane Reini ületama ja Prantsusmaa kagupiiri ähvardav teine Austria vägi ei olnud veel otsene oht, pidi Napoleon siiski mõned hädavajalikud jõud paigutama positsioonidele, kus nad said kaitsta Prantsusmaad teiste koalitsiooni vägede vastu, olenemata Waterloo kampaania tulemusest.