When the French retreated to the Marne in 1914, their strategy proved shrewd and salutary. For the Polish armies to fall back from the Corridor and East Prussia to a primary defense line from Loruń south through Lódź and Kielce to Cracow, and after that to the angle between the Bug and Vistula Rivers in the north and the Industrial Triangle (Cracow to Lublin to Lwow) in the south, was the strategy approved for Marshal Smigly-Rydz by his Allied military advisers (see map, p. 16). He need endanger only 15 Polish divisions by this plan, holding 45 in reserve to smite the Germans after their supply lines and communications were extended. His own defense line would be less than 500 miles long instead of more than 1,000 miles. Even the Germans estimated it would take them one month to crush Poland in such a campaign.
This week, after only eleven days of fighting, it was a grave question whether Poland was not already crushed. Perhaps Marshal Smigly-Rydz was to blame, for having his generals resist too long; perhaps the speed and power of the German advance surpassed even German calculations; perhaps the weather made the difference, staying dry and leaving the roads passable for motorized advance; perhaps the German air-power exceeded all expectations, breaking Poland's wings before they left the ground, smashing defensive positions before they could be organized. Certainly all these factors combined to make half Poland a shambles and her stand at Warsaw a desperate siege, as ghastly as Madrid.
Germany's armies from East Prussia, with the shortest distance to go, were the slowest to blast their way to Warsaw's outer defenses. Impeded at the Narew River after taking Plonsk and Pultusk, they were halted last week at the Bug. At the junction of the Narew and the Vistula, the fort city of Modlin had yet to fall at week's end. But artillery diverted for this defense weakened the Poles on the southwest. Smashing into Cracow, Germany's armies of the south swept on into the Industrial Triangle to take Sandomierz, Poland's munitions centre. Mechanized columns, whirling far ahead of infantry following in trucks, seized Kielce, Radom, Lódź (the textile centre). The entry of one motorized unit, traveling far ahead of its support, into the heart of Warsaw, led to premature announcement of the capital's invasion on Friday. Snipers at windows, machine gunners on roofs, drove the invaders back to Warsaw's southwestern suburbs, but there the main German forces soon arrived, too, and Warsaw was hemmed in on at least two sides. To its defense from the west came Polish divisions retreating in good order out of the big pocket formed around Poznan, where the Nazi attack had been light for fear of harming the thick German population. With other reinforcements from the east, Warsaw's defenders dug in on the Vistula's right bank, lobbing their shells over the city at the gathering Germans.
While the battle for Warsaw took form, in the south the German columns smashed on westward toward Lublin and toward Przemysl on the San River, gateway through the hills toward Lwow. Slovakian columns, too, came out of the border mountains to threaten Lwow, for through that city ran Poland's one remaining lifeline; the road and railroad to Rumania.