"He is a son of a big soldier who has ten thousands of soldiers force in his hands." Okay, so the double "a" here is a little awkward. Here's how I would write it: "He is the son of a big soldier who has ten thousands of soldiers force in his hands." Next, "ten thousands of soldiers force in his hands" doesn't work at all. "He is the son of a big soldier with a force of ten thousand soldiers." "If we are to fight them in a war, we’re at disadvantage because we only have thousand soldiers." Next you're missing articles in this sentence ^ "If we are to fight them in a war, we’re at a disadvantage because we only have a thousand soldiers." An English speaker would emphasize the smallness of a thousand soldiers by saying "one thousand soldiers" instead of "a thousand soldiers." Also, it reads more naturally if the subclause "we're at a disadvantage" has the future tense (because this is a conditional). "He is a son of a big soldier" Finally, returning to the first sentence, what is "big" doing here? I think you mean famous or successful. I would use one of those words. "He is the son of a famous soldier with a force of ten thousand soldiers. If we are to fight them in a war, we'll be at a disadvantage because we only have one thousand soldiers."