The Macedonian theatre of war was by common consent regarded as the most important, and Bulgaria here promised Serbia the assistance of 100,000 men. The Turks meanwhile were aware that all was not what it seemed beyond the frontiers, and in August 1912 began collecting troops in Thrace, ostensibly for manoeuvres. During the month of September the patience of the four Governments of Greece, Bulgaria, Serbia, and Montenegro, which had for years with the utmost self-control been passively watching the awful sufferings of their compatriots under Turkish misrule, gradually became exhausted. On September 28 the four Balkan Governments informed Russia that the Balkan League was an accomplished fact, and on the 30th the representatives of all four signed the alliance, and mobilization was ordered in Greece, Bulgaria, and Serbia. The population of Montenegro was habitually on a war footing, and it was left to the mountain kingdom from its geographically favourable position to open hostilities. On October 8 Montenegro declared war on Turkey, and after a series of brilliant successes along the frontier its forces settled down to the wearisome and arduous siege of Scutari with its impregnable sentinel, Mount Taraboš, converted into a modern fortress; the unaccustomed nature of these tasks, to which the Montenegrin troops, used to the adventures of irregular warfare, were little suited, tried the valour and patience of the intrepid mountaineers to the utmost. By that time Europe was in a ferment, and both Russia and Austria, amazed at having the initiative in the regulation of Balkan affairs wrested from them, showered on the Balkan capitals threats and protests, which for once in a way were neglected.