Complex sentence: Of more immediate value were enormous equipment stockpiles, including 20,000 Brown Bess muskets, which enabled Soult to repair his army's material deficiencies and to proceed with the projected invasion of Portugal.
Split into simpler sentences: Of more immediate value were enormous equipment stockpiles, including 20,000 Brown Bess muskets. This windfall enabled Soult to make good of his army's material deficiencies and to proceed with the projected invasion of Portugal.