next day the Germans had to retreat from Suwalki
and withdraw the lines that they had extended northward, and fall back
behind their frontier. This meant the end of the German attempt to cross
the Niemen and the beginning of the second invasion of East Prussia.

CHAPTER LXXVI

SECOND RUSSIAN INVASION OF EAST PRUSSIA

Wonderful as had been Von Hindenburg's accomplishment in defeating the
Russians and practically destroying one of their first-line armies, the
latter's recuperative power was almost as surprising. Deprived of the
prize of three weeks' fighting, defeated, and driven by the enemy on
their entire front for a depth of fifty miles into their own country,
they were nevertheless ready in a few days for a new offensive.
Undoubtedly this was partly due to the talent of their new commander,
General Russky, who had been sent up from Galicia, where he had gathered
experience as well as honors. But more so was it due to the protecting
defenses of the Niemen and the opportunities they offered for
reorganization, rest, and the collection of new forces.

The situation which was faced on the first week of October, 1914, was
perilous to all the armies engaged. Russia's fortresses on its eastern
front were concerned for a twofold purpose. In the first place, they
were to lend increased power of resistance to whatever means of defense
nature had provided, and this function, of course, determined their
location. Wherever rivers or other natural obstacles would offer
themselves to an invading enemy, there Russia had added especially
strong artificial defenses.

Any army invading Russia from East Prussia in a southerly direction
would have to cross the Narew River and its principal tributary on the
right, the Bober. These two run, roughly speaking, parallel to the
Russo-German border at a distance of about thirty to thirty-five miles,
and no army attempting an invasion east of the Vistula and south of the
Niemen could advance farther than this short distance without first
crossing the Narew and Bober.

The group of fortresses along this natural line of defense begins
opposite the southwestern corner of East Prussia with Osowiec, situated
on the railroad that runs from Lyck Bialistock. Thence it stretches in a
southwesterly direction through Lomsha, Ostrolenka, Rozan, Pultusk to
Novo Georgievsk, which latter is the most important of these, commanding
as it does the conflux of the Narew, Wkra, and Vistula rivers.