I'm having a hard time with participles, perhaps I don't really understand their purpose. I guess it has something to do with using a verb as an adjective and isn't the main verb...
Here is attempt a translating (I'll check the key later, for now I'm still trying to piece it together):
The army was in very great danger while marching through the enemies country.
The subject: army exercitus
very great: superlative of magna: maximus, I assume it has to agree with periculum (neuter) maximum
since the army is in danger, does something need to be in ablative form?
The army is singular so I would use erat for was,or is it one of these new evil forms of sum I just learned esset? (considering how important the sum family is to basic reading, I wish the book spent some extra time on them, i think I will have to look into doing that on my own)
the while marching is the participle part? is there some reason I can't use some combination of dum iter faciebant does this have anything to do with the subjunctive forms (which were in the previous chapter)
since I know this is a participle exercise, I'll go with iter facians , active present participle of facio
through enemies country: per hostis (genetive plural) finis (plural acc, even though country is singular, fines has to be in plural to be used as territory/country or is there a better word? I kind of like putting the noun finis, right after the preposition, (since they're going through the country, not the enemy) per finis hostis does this matter?
So my final answer is:
Exercitus maximum periculum erat per finis hostis iter facians.
Is this close?