I’m having some trouble with this, but I think I’m on the right track:
Alco insciis Saguntinis, precibus aliquid moturum ratus, cum ad Hannibalem noctu transisset, postquam nihil lacrimae mouebant condicionesque tristes, ut ab irato uictore, ferebantur, transfuga ex oratore factus apud hostem mansit, moriturum adfirmans qui sub condicionibus iis de pace ageret.
(“Alco, unknown to the Saguntines, thinking he could move anybody with pleas, when he had gone over to Hannibal at night, after tears and grim conditions could not move (Hannibal), that (under) what terms were being proposed by the irate victor he would (have to) be made a deserter of an orator and remain among the enemy, maintaining that whoever made peace under such conditions would die.”)
This all makes sense in the abstract and I think it’s the thought of the sentence but structurally it’s a mess. There’s a cum- and an ut-clause I can’t account for and, probably more fundamentally, I’m having trouble finding a main verb to go with “Alco” to form the predicate in the jungle of subordinate clauses. “Adfirmans” is nominative and “Alco” is its antecedent, so maybe the main clause is “Alco (was) maintaining that whoever made peace under such conditions would die”? I think I’ve got the rest of the chapter.
Ed: the “ut” clause makes more sense if you get rid of the commas around “ferebantur”. Ed2: I think I’ve got the “cum” clause, too – actually really simple.