Complex sentence: Although producing a relatively large and efficiently organised army, the Covenanters were relatively hastily assembled, and short of money and supplies, having to make assessments on parishes and relying on loans from Edinburgh merchants, making a long campaign difficult to sustain.
Split into simpler sentences: Although producing a relatively large and efficiently organised army, it was hastily assembled, and short of money and supplies. The Covenanting regime had to make assessments on parishes and relyed on loans from Edinburgh merchants, making a long campaign difficult to sustain.