Si milites ordinem servant, hostes vincere possunt.

Si means if. It introduces the condition:

si milites ordinem servant = if the soldiers keep/maintain order

The rest of the sentence gives the result:

hostes vincere possunt = they can defeat the enemy/enemies

So the whole sentence is a basic if ... then ... statement.

Milites is nominative plural of miles (soldier).

It is nominative because it is the subject of servant:

• milites servant = the soldiers keep

It is also the understood subject of possunt and vincere later in the sentence.

Literally, it means they keep order or they preserve formation.

• ordinem = order, rank, line, or formation
• servant = they keep, preserve, maintain

In a military context, ordinem servare often means something like:

• keep formation
• hold the line
• maintain discipline/order

Also, servant here comes from servare (to keep, preserve), not from servire (to serve).

Because it is the direct object of servant.

The soldiers are doing the action of keeping, and order/formation is what they are keeping.

So:

• milites = subject
• ordinem = direct object

Because it depends on possunt.

Latin uses an infinitive after possum (to be able, can):

• possunt vincere = they are able to defeat / they can defeat

This is just like English can defeat, except Latin uses the infinitive vincere where English uses the bare verb defeat.

Because Latin infinitives are single words.

In English, we often identify the infinitive with to, as in to conquer or to defeat. In Latin, the infinitive is built into the form itself:

• vincere = to conquer / to defeat

So Latin does not need a separate word meaning to here.

The subject is still milites (the soldiers), even though the word is not repeated.

So the sentence works like this:

• If the soldiers keep formation, [the soldiers] can defeat the enemy.

Latin often leaves out a repeated subject when it is already clear from the context.

Because the verb ending already tells you that the subject is they.

• servant = they keep
• possunt = they can

The -nt ending shows third person plural. Latin often does not need a separate pronoun unless the writer wants emphasis.

In the intended meaning of this sentence, hostes is accusative plural, the direct object of vincere:

• hostes vincere = to defeat the enemies / the enemy

A useful thing to know is that hostes can look the same in both:

• nominative plural
• accusative plural

So the form itself is ambiguous, but the meaning and structure here show that it is being used as the object.

Literally, hostes is plural, so enemies.

But in military English, we often say the enemy as a collective singular. So a translation like defeat the enemy can still be perfectly natural.

So both ideas are possible in translation, depending on style:

• defeat the enemies
• defeat the enemy

Latin word order is much more flexible than English word order because the case endings show what each word is doing.

So Latin can say:

• hostes vincere possunt
• possunt hostes vincere
• hostes possunt vincere

and the basic meaning can stay the same.

Putting possunt at the end is very normal Latin style. Word order is often used for emphasis, rhythm, or style rather than strict grammar.

The present tense here gives a general condition or general truth:

• If soldiers keep formation, they can defeat the enemy.

It does not have to mean only right now. It can mean something like:

• whenever soldiers maintain order, they are able to win
• as a general rule, discipline leads to victory

So the present tense works well for a broad, factual statement.