Complex sentence: This smokeless gunpowder called Poudre B (Gunpowder B) was made of stabilized nitrocellulose and had just been invented and developed in 1884 by Paul Vieille (1854--1934).
Split into simpler sentences: This smokeless gunpowder called Poudre B (Gunpowder B) was made of stabilized nitrocellulose. It had just been invented and developed in 1884 by Paul Vieille (1854--1934).