From its wellspring a half-mile high in the Carpathian Mountains, the San River’s narrow tributaries (see above) converge into a wide, winding defensive barrier across Galicia. The Russian Army, which is evacuating from the Carpathian passes that it bled so much to gain over the Winter, has decided to stand at the San and buy time for their retreating comrades. General August von Mackensen, whose new offensive has already overpowered and crushed one Russian army, knows his enemy’s intentions thanks to radio intercepts, and consequently knows exactly where and when to attack.
Last night under heavy pressure, the Russians evacuated three divisions from Jaroslau, whose Jewish population was especially relieved to welcome the Alexander Regiment, warning them that the Russians had wired the bridge for demolition. Moments later, the defenders detonated their charges, forcing the unit to use their boats in a crossing three hundred meters north of the bridge today. Crossing this afternoon under supporting artillery fire, the Elisabeth Regiment’s Fusilier Battalion is followed by the 1st Battalion; as they beat off a Russian counterattack, the 2nd Battalion crosses, linking up with the Alexander Regiment.
And there the offensive seems to pause, for Mackensen’s Eleventh Army is down to just over 11,000 shells of all types, with acute shortages of larger caliber shells — especially the 210 millimeter howitzer rounds that are so useful in destroying trenches. More than sixty miles from his starting-point in Western Galicia, and ninety miles beyond his railhead, it will take days of feverish work to get the requisite heavy guns and mountain of high explosive shells into place for what comes next.
Today ends a series of advances made by Mackensen’s army group towards Jaroslau and Radymno during the last five days. He has already torn a 185-mile long hole in the Russian line, splitting the Eastern Front in two. A transitional figure between the Second Reich and the Third, Mackensen is fighting on the same ground where Hitler’s armies will destroy Poland’s army at the outbreak of a Second World War. Shifting his mass from right to left over the next six days without losing contact with the foe, Mackensen will cross the San, once again knocking Russia off balance. In planning and organization, that future German-Austrian force will consciously mirror Mackensen’s achievement in establishing the bridgehead over the San today.
According to Clausewitz, there are three main factors in the success or failure of a defense along a river: the width of the water, the forces and means available to bridge the river, and the state of the defending force. The San is wide as it flows through the plains, marking the modern boundary of Poland and Ukraine, but it is not wide enough to stop Mackensen from crossing.
As many as 170,000 Russians have surrendered during Mackensen’s offensive, and more than 230,000 have been killed or wounded. He has captured hundreds of Russian guns and machine guns, adding to Russian procurement woes in weapons and ammunition. Already in a strategic rout along its southern flank, Russia appears to be collapsing. Yet this breakthrough has come at a cost of men and machines, a balance that Mackensen must make good before attacking again, and then make up again after the next thrust. By the end of his brilliant offensive, half his force will be casualties themselves.
This brings us to the second factor, namely Mackensen’s logistical problem. The roads in this part of Galicia are hardly the best, and war is destroying them with heavy traffic. The Central Powers have requisitioned all available motor vehicles for their columns, but there are still not enough of them, and they are so disparate in brand and model as to provide a supply and spare parts nightmare for any motor pool sergeant. Tens of thousands of horses also pull guns and wagons, as well as pontoon boats for bridging. To make such an operation remotely possible, Mackensen imposes stringent traffic-control measures.