Browsing Google Books' selection of Life magazine revealed a series of articles and maps that offer insight into how the European Front of the Second World War was "suppose to" have been fought. The magazine articles from September 1939 reveal two key errors. First was the assumption that France and the United Kingdom would actively try to save Poland. Second, Life committed the same judgment error that many generals did in thinking the war would be defensive a la World War I and not the lightening war the German's had planned.
The whole thesis of "Europe: Could Poland's friends break Axis wall in time to save her?", written right before the start of the war, is that the Western European Allies would struggle to open up a new front to save Poland. This theme is continued "War Plans in Mediterranean" which touches on a proposed British plan to go through the Black Sea and into Romania to reach Poland. Instead, after a brief raid into the Saarland, both Western Allies and Axis powers sat facing each other in what was known as the Phoney War. Unwillingness to fight combined with the shock of Soviet involvement in the invasion of Poland paralyzed the Allies into the sitting out their commitments and therefore allow Hitler to build up for the Blitzkrieg.
The other misconception was that World War II was going to be defensive, trench-like warfare in the mold of World War I. The Life quote says it best "the two fundamental facts of the situation are... 2) modern warfare gives a great advantage to the defense." The thought of mobile warfare, blitzkrieg, which targets not sitting locations but instead values movement, striking deeper targets, and collapsing the enemy from the rear had yet to become a reality on the strategic battlefield. Instead, maps of the Maginot and Siegfried lines reinforced the idea of juggernauts keeping each other in check. The maps' caption sums up the upcoming believed battle plan as such, ""Instead, they [the French] appeared to be getting into position for a long siege, an artillery-hammering war of attrition in which Allied superior material resources would eventually wear down the Germans' resistance." Instead the French waited and later the Germans used geography to go around and over the Maginot Line and crush France.