Complex sentence: Around the same time long-range patrols, each of about thirty men, went into the south and south-east of the Sinai desert to detect any Ottoman incursion into the area.
Split into simpler sentences: Around the same time long-range patrols, each of about thirty men, were sent into the south and south-east of the Sinai desert. Their objective was to detect any Ottoman incursion into the area.