Complex sentence: The Solothurn S-18/1000 20 mm Anti-Tank Cannon was a Swiss & German anti-tank rifle used during the Second World War, and was a variant of the earlier S-18/100 with modifications for a higher muzzle velocity, as well as a larger cartridge size.
Split into simpler sentences: The Solothurn S-18/1000 20 mm Anti-Tank Cannon was a Swiss and German anti-tank rifle used during the Second World War. It was a variant of the earlier S-18/100 with modifications for a higher muzzle velocity, as well as a larger cartridge size.