Could this sentence also mean "In order to surround the city, we need more warriors." (instead of many)? If not, how would you say "We need more warriors!".
law' means be many, not more. To say more, you can use the noun latlh additional one, another one. latlh SuvwI' DIpoQ We need additional warriors.
David knows this, but for all you Klingon learners out there, compare:
latlh SuvwI' wIpoQ We need an additional warrior.