What important developments are announced in Act 5, Scene 2 of Macbeth?

In a country setting near Dunsinane, soldiers with Menteith, Caitness, Angus and Lennox enter the scene with a drum and colors. They speak of meeting with Malcolm and the English General Siward near Birnam wood. The English soldiers are young and untried. Macbeth, in his highly fortified castle in Dunsinane, seems possessed by an fiery range, Angus speaks of Macbeth's guilt over his "secret murders." They and their soldiers will purge Macbeth of his illness- through a righteous war!