parts of the Kingdom of Dalmatia that had been promised to it under the secret Treaty of London. On 1 December 1918 the unification of the State of Slovenes, Croats and Serbs with the Kingdom of Serbia was declared, forming the Kingdom of Serbs, Croats and Slovenes. The Kingdom of Montenegro had already united with Serbia five days earlier. This declaration and firm action by armed groups halted any further encroachments by Italy. The National Council subsequently organised a celebration in Zagreb on 5 December with a Te Deum at the Zagreb Cathedral. Members of the 25th Croatian Home Guard Infantry Regiment and the 53rd Infantry Division held a protest at the same time at the nearby Ban Jelačić Square. The protest was quelled by the police with 15 dead and 17 injured. Both units were subsequently demobilised and disbanded. Formation to 1926 At the end of 1918, a Serbian Army mission led by Milan Pribićević, Dušan Simović and Milisav Antonijević arrived in Zagreb to lead the re-organisation of the Serbian Army and the National Army of Slovenes, Croats and Serbs into a single new Army of the Kingdom of Serbs, Croats and Slovenes (KSCS). The Serbian Army numbered 145,225 soldiers at the end of the war, and absorbed the some 15,000 former Austro-Hungarian officers and volunteers which had been organized by the National Council. By 1 January 1919, a total of 134 former high-ranking Austro-Hungarian officers had been retired or relieved of their duties. From late 1918 until 10 September 1919, the new army was involved in a sharp military confrontation with irregular pro-Austrian formations in the region of Carinthia on the northern frontier of the new KSCS. At one point, KSCS troops briefly occupied Klagenfurt. After a plebiscite in October 1920 the frontier with Austria was fixed and tensions subsided. To deal with these security concerns, a large mobilization was carried out from 1918 to 1919, reaching a peak of 450,000 soldiers in July 1919, though demobilization quickly followed. By early 1921 the army organisation had settled into one cavalry division of four regiments, 16 infantry divisions, each consisting of three infantry regiments and one artillery regiment, and additional army-level troops. The 16 infantry divisions were grouped into four numbered army areas, with headquarters at Novi Sad (1st Army), Sarajevo (2nd Army), Skoplje (3rd Army), and Zagreb (4th Army). Later in 1921, a second cavalry division was formed