A real war and a "war" of fighting to grow old and successful
Explanation:
Based on the excerpt, Robert Louis Stevenson was reminiscing about his days as a younger man and the internal conflicts he had.
In the first paragraph, he talked about the real war he witnessed where he heard the "loudness" of the battles and the "pain of men's wounds". He also talked about another internal "war" which had to do with "slavery of competition", toiling for years and which culminated to fighting to be old and successful.
The answer is rowdy. Rowdy means noisy or disorderly, which is what the term boisterous is most likely to mean in this sentence. Shouting, cheering, and laughter could all go under the category of rowdy.
