Come in Lieutenant.
An insult from who? The Army of the S? What is the S standing for? Shambles, Shabby, Scabrous?
You say you have a picture/poster of the fellow that issued the challenge. Lets see:

Oh yes I remember him well - that's Drex the Jester. When I was at the Point in the old days we used to see this clown and his circus when they came to town. Our intelligence has advised that he is now a Yank general - well I guess that is an improvement on those people they have sent against us up until now. Let's have a look at those intel pics that you have brought:

THE AotS on the Move

AotS ARTILLERY
Let's call our officers....Hey Boys get a load of these "soldiers". The Yanks are really scraping the bottom of the barrel. Send for the latrine detail - they should be able to rid us of this irritation.
Oh there's more pics:

YANK CAVALRY - Whatever is he doing?

MORE YANK CAVALRY

AND YET MORE - That one's in full dress uniform
You say there is a K9 unit too?

DOGGONE!
OK Lieutenant tell Drex the Jester the ANV is delighted to meet him and his "Boys". Should be a good laugh if nothing else.