The Saar Offensive was a French operation into Saarland on the German 1st Army defence sector in the early stages of World War II. The purpose of the attack was to assist Poland, which was then under attack. However, the assault was stopped and the French forces withdrew.

According to the Franco-Polish military convention, the French Army was to start preparations for the major offensive three days after mobilisation started. The French forces were to effectively gain control over the area between the French border and the German lines and were to probe the German defenses. On the 15th day of the mobilization (that is on 16 September), the French Army was to start a full-scale assault on Germany. The preemptive mobilization was started in France on August 26 and on September 1 full mobilization was declared.

French mobilization suffered from an inherently out of date system. The French military′s ordnance lacked the tanks and planes of the mechanized German military which greatly affected their ability to swiftly deploy their forces on the field. French command still believed in tactics of the previous war which relied heavily on stationary artillery which took time to transport and deploy (many pieces also had to be retrieved from storage before any advance could be made).