Short answers, pulled from the story.
The Saar Offensive was a French military invasion of the German region of Saarland that ran from the 7th of September to the 16th of October 1939. It was launched in response to the German invasion of Poland on the 1st of September 1939, under the terms of a 1921 Franco-Polish military convention.
The original plan called for 40 divisions, one armored division, three mechanised divisions, 78 artillery regiments, and 40 tank battalions. In practice, only eleven French divisions from the Second Army Group actually advanced, moving along a 32-kilometre stretch near Saarbrücken.
France halted the offensive after the Anglo-French Supreme War Council met at Abbeville on the 12th of September and ordered all offensive action to stop. General Maurice Gamelin then ordered forces to withdraw to the Maginot Line on the 21st of September, without notifying Poland. The 40-division assault Poland's Plan West had depended on never materialised.
German military commander Alfred Jodl testified at the Nuremberg Trials that Germany did not collapse in 1939 "only" because the approximately 110 French and British divisions in the west remained completely inactive against 23 German divisions. General Siegfried Westphal added that a full French attack in September 1939 would have allowed the German army to hold out for just one or two weeks.
French forces advanced up to 8 kilometres into German territory in some areas and captured about twelve towns and villages, including Gersheim, Kleinblittersdorf, and Brenschelbach. They also occupied most of the Warndt Forest, roughly 7 square kilometres of heavily mined terrain, but stopped short of the Siegfried Line.
French casualties across the offensive totalled around 2,000, counted as killed, wounded, or sick. German records acknowledged 196 soldiers killed, 114 missing, and 356 wounded, along with eleven aircraft shot down as of the 17th of October 1939.