After the Eleventh Battle of the Isonzo matters on the Isonzo front changed drastically. This happened not because the Italian army had succeeded in its advance towards the arid Bainsizza plateau but because Germany chose to take an active part in favour of the Habsburg allies. The German military command was in fact aware of the very serious crisis that Austria-Hungary was going through: since there were no more reserve forces, the next attack could break the front and allow the Italians to spread out towards Trieste: "It is necessary to save Trieste, even with German aid, if no other way is possible." (Paul von Hindenburg, Della mia vita, Stabilimento poligrafico per l'amministrazione della guerra, Rome, 1923 in Mark Thompson La guerra bianca, Il Saggiatore, Milan, 2009, page 300).
On the other hand even the Austro-Hungarian leadership knew that without help it would be unable to continue the war in Italy. In the last few days of August Charles I wrote a letter to his German counterpart, Kaiser Wilhelm II, to inform him that a new battle on the Isonzo front would have fatal consequences. The military commanders, even more explicitly than their own emperor, asked for help from the German allies for an offensive that would anticipate the moves of the Italians. The German Chiefs of Staff, Paul von Hindenburg and Erich Ludendorff, accepted and took into consideration the proposal of an attack between the zone of Plezzo (today known as Bovec) and Tolmino. Since this involved mountainous terrain, they sent Lieutenant General Konrad Krafft von Dellmesingen, a military expert in warfare on this type of terrain.
In theory the objective that was established was extremely ambitious: the aim was to push the Italians back to the pre-war boundary line and, with luck, perhaps even reach the river Tagliamento. In order to do this, it was planned to launch an attack on the line Plezzo-Saga to the north of Caporetto and then on the whole line stretching some 25 kilometres up to the bridgehead at Tolmino. This breakthrough would have allowed access to the village of Caporetto and this in turn would have opened the way towards Natisone Valleys and the Friuli plateau.
In a few weeks the preparations for the attack were completed swiftly, precisely and shrewdly. Hindenburg set up the 14th Army consisting of seven German divisions and three Austrian divisions under the leadership of the German General Otto von Below, supported by seven other reserve divisions and more than one thousand cannons. Many German soldiers reached Tolmino disguised as Austro-Hungarians while others were transferred at first publicly in Trentino and then secretly on the Upper Isonzo. Moreover, a strong anti-Italian propaganda campaign raised considerably the morale of the soldiers, ready for their first offensive action on this front.
A really new aspect in preparations for this battle consisted in the tactical approach that was established by the German military commanders and that had already been adopted with good results on the eastern and western fronts. These tactics envisaged a short but very intense battle preceded by a sustained and accurate bombardment. This strategy would create conditions for penetration by the infantry at only one point that would then at a later stage be extended behind the enemy lines: "like a punch released against a barrier so that later the palm will be opened and the fingers will spread out." (Fritz Weber, Dal Monte Nero a Caporetto - Le dodici battaglie dell'Isonzo 1915-1917, Mursia, Milan, 1994, page 382).
