Near the end of June, there was briefly some hope that the Poles might actually be able to hold off the Soviets. They had, after all, not penetrated very far, and seemed tentative, which could be mistaken for cowardice or lack of faith. Some generals even began to think perhaps Poland might survive which, ironically, caused some consternation among other generals, because many key points in the German main war plan were contingent upon the expectation of an eventual fall of Poland.
But then, once the Soviet spearheads began moving, and especially once units began being trapped behind the lines, expectations returned to normalcy. Some generals, however, began to suggest moving German defensive lines forward, in light of how long it was taking for the Soviets to crash through Poland, and also in consideration for once that country fell, that Germany might not be driven back upon her own borders immediately.
Entering into these considerations, naturally, was the sorry state of Germany's Energy stockpiles, which had been caught at a low ebb when war began, and which was dwindling by nearly 300 units per day. Attention was drawn to the Polish city of Krakow, which not only was a respectable industrial center, but which also produced a significant amount of valuable Coal.
The red spot on the above map shows Krakow, which some generals suggested should be placed behind the German defensive lines. If done, then the Vistula River might also form the advance line, but from there things became complicated. A more conservative plan would be to advance to hills around Wisla (the beige dot on the far south), and from there also use the forests of Polish and German Silesia (the green dots) to complete a slightly more forward-located defensive line.
Further east, what had started as a pronounced spearhead into the Polish lines had settled into a more uniform line of steady advance. The key Polish city of Lvov lay along its path, and there seemed no great likelihood that a sufficient stand could be made by the Poles to prevent its fall within a week or so.
Just in time for action, German engineers developed a new style of portable river-crossing bridge, which would come in handy if we had to fight across these rivers.
And, around this time (negotiations were speeded by the initial Polish resolve, and had not had time to fall apart on more recent news), Yugoslavia decided that she felt threatened enough, and confident enough in Germany's abilities, to join the Axis alliance against the USSR. This provided Germany with an important and militarily strong ally, to combine with the others, including Italy. But the most obvious catch in this great news was that Austria remained neutral, and no one could cross into Germany to assist unless either Austria, or Czechoslovakia, or Romania joined in the war. Some German generals were reminded that plans remained on the table to force Austria's cession into the Greater Reich, and these suggestions were not entirely ignored.
On 10 July, the Soviets made a probe against the German defenses at Goldap, East Prussia. They had been enjoying such success against the Poles, who were now fleeing in all directions, that they apparently decided it was time to test Germany, and see what kind of enemy would be found there. It did not help Germany's initial reaction that supply was such a difficulty in East Prussia, and so the Germans began at a disadvantage.
However, we met the attack, which was not wholly unexpected, vigorously. The fixed fortresses were not as helpful as some might have hoped, but the entire German formation was heavily entrenched, and the defense was ably led by General von Kortzfleisch, who had combat experience from Spain. After two days, the Soviets decided they had tested Germany... and Germany had passed. They withdrew their forces, and continued south, deeper into Poland.
While this brief battle was underway, another threat came to the attention of the jittery General Staff, who were expecting the worst, in absence of more encouraging information. A Russian fleet had been located in the Baltic. Since transport ships were found to be in company, it was feared they were intending to mount an amphibious invasion along the vulnerable Baltic coast -- perhaps at Stettin, or Kiel. A frantic alert was sounded, and every resource was rushed to react.
In the end, the KMS Graf Spee, KMS Prinz Eugen, KMS Hipper and KMS Blucher were all immediately available to engage the Soviet fleet's transports, and its escorting cruisers and battleships. Their sortie was successful on a strategic level -- three transports were sunk, and a fourth was lost to German Condor torpedo bombers a day later -- but the German squadron was spent. Prinz Eugen and Blucher limped back to port, happy to have survived the fight. It would remain in port for a while, recovering and repairing, while its protective duties were assumed by stronger fleets (albeit, of older ships).
By the 15th of July, two indistinct spearheads in northern Poland were threatening to converge upon the city of Brest-Litovsk, which would also accomplish the task of encompassing and pocketing several Polish divisions, which were slow in retreating from their positions near the border with the USSR.
This was not an immediate danger, but German planners could see a trap being set, and expected that this would happen, eventually. The city of Grodno had fallen, and since this was the first city of major importance to fall, its surrender was the occasion of a great many concerns expressed that, perhaps, the Soviets would arrive against the German defensive lines before our rush-recruitment of garrisons and infantry were quite ready. Other generals counseled calm, and assured them this would not happen.
German defenses had been tested, but East Prussia held several strong, mobile divisions which were intended to mount a counteroffensive at some yet undetermined time. It was decided the time had come to test these offensive forces with a counterattack upon Suwalki -- a Polish city boasting an airfield and radar installations which Germany would prefer the Soviets not have access to.
Orders were issued to General Guderian, who assaulted the Soviet lines, with initial success against the surprised enemy. However, his attack had fallen upon an already tired division that had been pushing south. He delayed the Soviet advance, there, but other Russian units were pushing south, and when two more divisions, including light tanks, joined in the defense of Suwalki, it became apparent that German Panzer IIIs would be insufficient to break through or force the enemy back. The battle was ended with small loss on both sides.
By the 20th, the German Baltic coast was secure, and the borders of East Prussia seemed so also. But Poland was collapsing. Brest-Litovsk was now on the front lines, and though most Polish units had escaped the closing pincers, at least a couple had become trapped.
Another potential pocket was being formed in the center of the Polish lines, and the city of Lvov had fallen, in the south. Some predicted the Soviets would be on the banks of the Vistula within a week, others said by the end of the month. In reality, the Soviet advance was slowing, partially due to supply difficulties, but their advance was inexorable.
Near the end of July, several advances in tank technology had been developed, and were being rushed into action on the new Panzer IV models which had recently been deployed. Two divisions which had been recently sited in Pommerania to prepare for action were now asked to move into East Prussia in order to bolster the offensive capacity present there.
These Panzer IVs were being modified on the run with new technology, having been given priority for upgrades.
General Rommel was passing Johannesburg, en route further east, when the Soviets caused some small alarm. They had advanced south and west from Suwalki so quickly that German observers had not realized they were in a position to outflank the East Prussian defensive "wall" (our level 1 fortresses) and enter East Prussia from the south.
They did this, seizing the town of Johannesburg, just as Rommel's two divisions were passing by. Nothing in this was unexpected according to German defensive plans, though it was a bit startling to have German territory invaded by the Soviet Union for the first time. Rommel was in a position to do something about this, but there was some disagreement as to what the best reactive action might be. German offensive forces in East Prussia, as had been seen, were limited in number.
Should they hold the line, preventing further incursions, or undertake a counterattack of one nature or the other?