On September 9 the army victorious at Osterode ten days before (and believed to consist of eleven corps) commenced a general advance along the East Prussian front into Russian Poland. For several days subsequent to his retreat, Rennenkampf had remained stationary along a line traversing the railway at right angles between Königsberg and Insterburg. This position he clung to tenaciously until noon of September 10, when the long-ranging shell-fire of the German fortress guns which were being used for the purpose, together with a powerful turning movement around their left flank, obliged the Russians to continue their retreat. They fell back on the 11th-12th in a northerly direction slightly east of Wirballen, where a fresh stand was made. Although the scene of action had now been transferred from German to Russian territory, the advantage was by no means wholly with the Teutons. They found themselves operating in a strange and unfriendly region, and one in which the railway system could not be of much use to them for the rapid transit of men and material, seeing that the German and Russian lines have different gauges. Moreover, Austria’s military misfortunes might now be deemed to have eliminated that Power from the problem. And Rennenkampf was resolved not to fight another pitched battle until he could do so under favourable auspices. Local incidents along this Russian-Polish frontier included the dropping of German bombs and proclamations into the town of Suwalki. By these bombs the railway-station and schoolhouse were damaged and one child was killed. The frontier town of Filipovo also suffered a partial bombardment. While Rennenkampf’s headquarters were at Insterburg, certain of the inhabitants of that place were caught red-handed in the act of signalling movements of troops to their “friend the enemy,” while in a few cases Russian troops were fired on from houses of the townspeople. Several of these irregular belligerents were put to death by sentence of a court-martial. Next morning a German aeroplane dropped in the Russian lines this audacious message addressed to Rennenkampf: “Your troops are shooting peaceful citizens. If this is done without your knowledge, stop it at once! If the troops are carrying out your orders, then know, General, that the blood of these innocent people falls on your head, and on yours alone.”