The 1939 Kasprzycki-Gamelin Convention called for France to launch an offensive into Germany within three weeks of hostilities breaking out between Germany and Poland. The French military went ahead with preparations for a major offensive and sent forces into the Saarland, a heavily industrialized region with significant coal production. Some forces advanced to within a few kilometers of the Siegfried Line, built opposite the Maginot Line. The Germans considered the Siegfried Line to be inadequate for its role due to labor and material shortages, with one general calling it “little more than a building site.” However, the French decided to call off the Saar Offensive in mid-September and withdrew back to the Maginot Line. Interestingly, the Offensive was initially planned for September 17, the same day the Soviet Invasion of Poland started. It seems unlikely the Saar Offensive would have changed the Soviet calculus regarding Poland, but perhaps it could have changed the outcome on the Western front. What would have happened if the French had gone ahead with the Saar Offensive?