Prima vigilia milites vallum iterum muniunt et aquam e fossa tollunt.

Prima vigilia is ablative singular.

• vigilia = watch (especially a watch of the night)
• prima = first, agreeing with vigilia in case, number, and gender

Latin often uses the ablative of time when without a preposition. So prima vigilia means:

• in the first watch
• during the first watch

This is why there is no separate Latin word for in here.

Because Latin frequently expresses time when with the ablative alone.

So English says:

• in the first watch
• during the first watch

But Latin can simply say:

• prima vigilia

This is a very common pattern with time expressions.

Here milites is the subject: the soldiers.

It is nominative plural.

A learner might hesitate because milites could also look like an accusative plural form in some contexts, but here the sentence structure makes it clear that it is the subject, because:

• muniunt = they fortify
• tollunt = they lift/remove

Both verbs are 3rd person plural, so they naturally go with milites as the subject.

The same subject, milites, goes with both verbs.

So the structure is:

• milites vallum iterum muniunt
• et aquam e fossa tollunt

In other words:

• the soldiers fortify the rampart again
• and remove water from the ditch

Latin often states the subject once and lets it apply to multiple verbs.

Vallum is accusative singular.

It is the direct object of muniunt, so it is the thing the soldiers are fortifying.

• muniunt vallum = they fortify the rampart

A vallum is not just any wall. In Roman military context, it usually means the rampart, palisade, or defensive earthwork of a camp.

Muniunt comes from munio, munire.

It means things like:

• fortify
• build up
• strengthen
• protect with defenses

Here muniunt vallum means they fortify the rampart or they strengthen the rampart.

Form:

• present tense
• active voice
• indicative mood
• 3rd person plural

So literally: they fortify.

Iterum is an adverb meaning again.

Here it modifies muniunt:

• vallum iterum muniunt = they fortify the rampart again

Latin adverbs are often quite flexible in position. Iterum could appear in a different place and still mean the same thing. Its position here is natural and clear, but not the only possible one.

Aquam is accusative singular.

It is the direct object of tollunt:

• aquam tollunt = they lift/remove the water

So in this sentence there are two accusative direct objects, each belonging to a different verb:

• vallum with muniunt
• aquam with tollunt

Fossa is ablative singular because it follows the preposition e.

• e / ex
  • ablative = out of / from

So:

• e fossa = from the ditch or out of the ditch

The noun fossa means ditch, trench, or excavated defensive ditch.

Both e and ex mean out of / from.

In many contexts they are basically interchangeable. Very often:

• ex is common before vowels
• e is common before consonants

Since fossa begins with a consonant, e fossa is perfectly normal.

You may still see ex fossa in Latin too; the choice is not always rigid.

Yes, tollunt comes from tollo, which often means:

• lift up
• raise
• take away
• remove

In this sentence, with aquam e fossa, the sense is best understood as:

• remove water from the ditch
• take water out of the ditch

So it may be literally lift, but in smooth English remove or draw out is usually better.

Both are present indicative active, 3rd person plural.

• muniunt = they fortify
• tollunt = they remove / lift

Depending on context, Latin present tense can sometimes be translated in different ways in English:

• simple present: they fortify
• vivid narrative present: they are fortifying or even historical present in a story

But grammatically, both forms are straightforward present tense forms.

Because Latin has no articles.

So Latin nouns by themselves can mean:

• a soldier / the soldier
• water / the water
• a ditch / the ditch

The translator decides from the context which English article sounds right.

So:

• milites = soldiers or the soldiers
• vallum = a rampart or the rampart
• fossa = a ditch or the ditch

Latin word order is much more flexible than English word order because the endings show the grammatical roles.

A more English-like order might be:

• Milites prima vigilia vallum iterum muniunt et aquam e fossa tollunt.

But the original begins with prima vigilia to set the scene immediately:

• During the first watch, the soldiers...

Putting the time phrase first is a very natural Latin choice.

Because prima agrees with vigilia in:

• gender: feminine
• number: singular
• case: ablative

This agreement shows that prima vigilia is one phrase: the first watch.

Latin adjectives usually match the nouns they describe in case, number, and gender.

A useful breakdown is:

• Prima vigilia = time expression
• milites = subject
• vallum = object of muniunt
• iterum = adverb
• muniunt = first verb
• et = and
• aquam = object of tollunt
• e fossa = prepositional phrase
• tollunt = second verb

So the sentence has:

• one time phrase
• one subject
• two coordinated verbs
• each verb with its own object

That makes it a good example of how Latin can pack a lot into one compact sentence.