Some modest results with spawn_army

[SigniferOne]

Maybe try with underscores instead of spaces, i.e. merc_numidian_cavalry, or else try to find some other identifiers for those units that are a single word. Clearly the game gets caught up by the fact that there's more than one word in the identifier, i.e. 1) merc 2) numidian 3) cavalry (because in the error, it shows you that it sees, and does not understand only the first word). Therefore, try to find ways in which to pass that unit in as a ONE word. If this is a general problem for the game to find it hard to process identifiers that consist of multiple words, then there MUST be a description somewhere where a single word is also assigned to the same army, OR it is assumed by convention that the multiple-word identifier is equivalent to some single-word version. Usually, in RTW, this means that

"word1 word2" = "word1_word2"