Complex sentence: This remained unchanged until May 1915 when Italy entered the war on the Entente side, at which point troops were deployed to the Unterengadin valley, Val Müstair and along the southern border.
Split into simpler sentences: This remained unchanged until May 1915 when Italy entered the war on the Entente side. At this point troops were deployed to the Unterengadin valley, Val Müstair and along the southern border.