Complex sentence: Up there in the mountains, the revolutionaries established their headquarters, which they fortified with trenches of big rocks, just like the way some upland farmers pile up big rocks on top of one another in their farms.
Split into simpler sentences: Up there in the mountains, the revolutionaries established their headquarters, which they fortified with trenches of big rocks. Just like the way some upland farmers pile up big rocks on top of another in their farms.