What kind of Genitive?

Oh, the questions kids ask these days.

I received this inquiry:

“Also, I had a few questions about the chapter.  In line 110, it says nec vallum ascendere.  I get the point that the Germans aren’t climbing the walls because the Romans are throwing spears at them, but how exactly should this be translated?  In the context of the sentence, it did not look like the accusative w/ the infinitive.  

On top of that, after reading this chapter I seem to understand that when the Romans talked about quantity, they used the genitive.  If they had two dogs, they said duos canum (two of the dogs).  This happens in lines 98 (sex milia militum) and 103 (duo milia passuum longum.  Quattuor portae).  However, in line 93 (mille passus) and line 96 (unus passus est quinque pedes), it doesn’t use the genitive.  What’s going on?  

Finally, you said castra is always plural.  Thus it uses plural verbs.  Line 94 says, “Castra sunt militum oppidum.”  This doesn’t make sense translated into English.  How should I translate it? “

Here is my reply:

As for your first question, it is not accusative + infinitive.  The entire sentence hinges on the verb possunt in line 109.  Illi autem nec pila in castra iacere possunt, quod fossa nimis lata et vallum nimis altum est, nec vallum ascendere…

Translate it as, “They are not able to throw the spears into the camp, because the ditch is too wide and the wall is too high, nor are they able to climb….

Now for the second question:

You have discovered something grammarians call the partitive genitive.  When refering to a part of something, or a part of a group, Latin will often use the genitive.  Two of the dogs refers to part of a group of dogs.  This is verb common with neuter nouns… and canis is neuter.  

With milia and all its forms Latin uses the genitive again.  This is called the genitive of the whole.  This is why you will see things like sex milia militium and duo milia passuum longum.  

As for quattuor portae, I will have to figure out what is going on there.  You have stumped me.

Castra is a weird word.  This video should help: https://www.youtube.com/watch?v=kG7GXmn5Yes

The sentece you are attempting to translate would be, “The camp is a military town.”  You could also translate it as “Camps are military towns.”