Complex sentence: The units are specialized in unconventional warfare and guerilla tactics and long range reconnaissance deep behind enemy lines, with no support from other units, in all weather conditions and in all terrain, for periods of up to 30 days.
Split into simpler sentences: The units are specialized in unconventional warfare and guerilla tactics and long range reconnaissance. This takes place deep behind enemy line, with no support from other units, in all weather conditions and in all terrain, for periods of up to 30 days.