Complex sentence: A majority of the materials used were cotton, wool, and silk for the fabrics, wood for weapon stocks, leather for ammunition pouches, belts, etc. But by 1943 material shortages caused much of the leather to be switched to cotton straps as a substitute.
Split into simpler sentences: A majority of the materials used were cotton, wool, and silk for the fabrics. Leather for ammunition pouches, belts, etc. But by 1943 material shortages caused much of the leather to switch to cotton straps as a substitute.