22nd April
For the first time, poisonous gas known as yperite was used by the Germans near Ypres.

26th April
London Treaty was agreed upon, promising Italy a large part of Primorska, Kvarner, Istria and Dalmatia with the islands, and lands in Southern Tyrol. Italy was obliged to open a new front against Austria-Hungary within a month. 

30th April
The Yugoslav Committee was established in Paris.

23rd May
Italy declared war on Austria-Hungary.

4th June
Italians selected sixty inhabitants of the villages Ladra, Smast and Kamno. Six of them accused of being traitors were shot without trial and the rest were interned. Similar thing happened in Vileš near Gradišče ob Soči a few days earlier.
 
16th June
Italian army conquered the peak of Krn.

23rd June – 7th July
First Battle of the Isonzo (Soča).

18th July – 3rd August
Second Battle of the Isonzo.

20th August, 1915
Italian planes bombarded Slovenian territory on Ajševica.

18th October – 4th November
Third Battle of the Isonzo.

10th November – 2nd December
Fourth Battle of the Isonzo.