…On May 9th the Italians resumed the offensive. The floods had mostly ended and they were ready to cross the Tagliamento. As usual parties of boatmen and Arditi infiltrated under the cover of a firewall and gas attack. Lodgments were made and pontoon bridges were thrown up. Unlike previous assaults there was not even an attempt at a major counterattack. Small local forces attempted attacks, but nothing larger than a battalion did so. The Austrian Army had been shattered in the previous offensive and its remnants could not effectively resist.
The front collapsed within 24 hours, with 20,000 prisoners taken and the Italians securing no less than six beachheads over the river. The only real hope the Austrians had to break the Italian offensive was the mountains surrounding the Venetian plain. Therefore the Austrians ordered a retreat while they tried some to establish some semblance of a defensive line on the alpine foothills. Italian pursuit was vigorous, but limited by the exhaustion of their air and motorized units, that had still not made good the losses from the earlier campaign. Despite that another 100,000 prisoners were taken before the Austrians reached the foothills on the 16th.
However that front was only one of their worries, Italian forces out of Albania had already liberated Montenegro on the 30th and captured Ragusa on the 8th. There were no forces available to stop them from heading inland to take Sarajevo where this all started or even to press on into Serbia and liberate that country. However given the relative distances involved and the infrastructure of the areas in question this front was of lesser importance, it could not threaten Austria. It could threaten Hungary, but already high command and the Kaiser were concerned about the loyalty of the Hungarians, and the logistics of attacking Hungary through Albania were difficult.
In any case the Italians had no interest in moving inland, they wanted to capture territory that was promised to them, not territory that would belong to Yugoslavia. Hence, they moved on to take Spoleto on the 13th, and Zara on the 18th, with naval elements moving to secure the islands behind them. Sarajevo was captured on the 19th as much for reasons of personal glory on the part of several mid-ranking officers than any real strategy.
In the north however the situation had turned critical. The Italians continued their pursuit even as the Austrians reached the foothills, with the ramshackle defense line that had been established not even being noticed by the advancing Italians. By the 18th it was clear that even the forces in the Alps were beginning to buckle, and the invasion of Austria proper was only days away.
Help was requested from Germany; however the Germans were in poor shape themselves. The Germans offered the transfer of the remaining Austrian forces on the Western front, however a half dozen heavily understrength divisions were not enough to turn the tide, even if they could be delivered quickly, which was no sure thing. There were German reserves in Bavaria that could potentially be enough to stop the Italians in concert with the Austrian troops from the Western front. However the Germans made it clear that one or the other would happen, but not both.
Without a promise of German help there would be no halting the Italian momentum. Things would only get worse from a perspective of their negotiating strength. Therefore on May 20th the Kaiser sent a request for an armistice to the Italians.
The Italians took almost 72 hours to respond to this message. Partially this was due to the internal political matters, but mostly in order to organize the occupation of the city of Trieste and the islands of Veglia, Cherso and Arbe by naval forces. On May 23rd the guns fell silent between Austria and Italy. Germany now stood alone.
-Excerpt from European Wars for Americans, Harper & Brothers, New York, 2004
Short but the end is nigh