North Kosovo crisis (2011–2013)
Clashes between the Republic of Kosovo and ethnic Serbs in northern Kosovo began on 25 July 2011 when the Kosovo Police crossed into the Serb-controlled municipalities of North Kosovo, to control several administrative border crossings. This was done without the Kosovo Police consulting either Serbia or Kosovo Force (KFOR)/EULEX (European Union Rule of Law Mission in Kosovo).
Source: Wikipedia — North Kosovo crisis (2011–2013) (CC BY-SA 4.0)