What did darius expect alexander to do?

He ordered his troops to be well fed and then to rest. Darius, on the other hand, mindful of Alexander's unpredictable manoeuvres, ordered his army to stand to throughout the night in readiness for a surprise attack. ... By overrunning the Persian Empire, Alexander helped extend Macedonian and Roman rule.

b. Stage a night attack

there is not all the infomation needed to answer this question.   we need the who was going, or we need to know what islands you are talking about.