It most certainly wasn't! For one thing, "alliance" is a feminine noun, so the adjective would be "ancienne", not "ancien".
And, ancien / ancienne has quite different meanings depending on whether it precedes or follows the noun it qualifies. If it comes before, then it means "former" or "previous", as in "mon ancien poste" = "my previous job" but when it follows the noun, it means "old" or "ancient".