At socii magna ducum... vincunt

[Biljana]

Hi, I'm having trouble translating this sentence from class text book:

At socii magna ducum et militum fortitudine Turni copias vincunt.

The best I could do was:
But the friends by leaders' (_____ greatness, or something like that?? trouble is, can't find in the dictionary similar noun that would fit) and soldiers' bravery conquer Turnus' multitudes.

Or, of course, something completely different...

Thanks in advance!

 

[Aurifex]

At socii magna ducum et militum fortitudine Turni copias vincunt.

But our allies overcame Turnus's forces thanks to the great courage of our soldiers and leaders.
ED. Sorry - it's present tense : ...our allies overcome.

 

[Biljana]

Great, thank you very much! So, we can translate "magna ducum" as "(great) courage of our leaders"?
I was confused by not being able to find in the dictionaries the noun "magna" as such, in order to put it in corresponding declension. So it does exist?
It would be big help if you could clarify that for me...

 

[cinefactus]

it is the adjective magnus-a-um and goes with fortitudine

 

[Biljana]

Aha, ok, now I get it! I was stuck with the idea that it somehow goes with ducum... Thank you!