Complex sentence: The Mle 1886 Lebel rifle is the first military firearm to inaugurate the use of smokeless gunpowder: this new propellant had just been invented in 1884 by French chemist Paul Vieille (1854--1934).
Split into simpler sentences: The Mle 1886 Lebel rifle is the first military firearm to inaugurate the use of smokeless gunpowder ammunition. This new propellant had just been invented in 1884 by French chemist Paul Vieille (1854--1934).