Attack on Titan use of 一体

Question

I am trying to translate a scene early on in Attack on Titan but having some trouble with one line.

Link to the scene in question

This is what I have so far:

総員戦闘用意

All units, prepare for battle

• 総員{そういん} - all members/all units
• 戦闘{せんとう} - battle
• 用意{ようい} - preperation

目標は一体だ

the objective is one body ?

I don't quite understand what is being said here. Are they saying their objective is to get 1 body, as in to kill 1 titan, Or is it more along the lines of "we are share the same objective" ?

• 目標{もくひょう} - mark; objective; target​
• 一体{いったい} - one object; one body; unity​

必ず仕留め

be sure to take it down

• 必{かなら}ず - always; without exception; necessarily; certainly; without fail; positively; invariably​
• 仕留{しと}め - to bring down (a bird); to kill​

ここを我々人類最初の壁外拠点とする

here we will make humankind's first base outside of the walls

• ここを我々{われわれ} - here we
• 人類{じんるい}最初{さいしょ}の - humankind's first
• 壁外{へきがい} - outside of the wall
• 拠点{きょてん}とする - to be based in (a place)​

Any general feedback is also most welcome.

Answer 1

Here 体 is just another counter for animals, robots, statues, etc, which is usable whether they are big or small. So "one titan", not "the same objective". I think 体 is preferred in contexts where you have to refer to things matter-of-factly. Using 匹 or 頭 would not be wrong, but they would feel less "objective". See: Why was "一匹" used for Godzilla?

Other parts of your translation look perfect to me.