The JNA was originally deployed in order to preserve Yugoslavia, and the initial plan of the campaign entailed the military occupation of Croatia and the removal of the Croatian leadership elected in 1990.

In early October, the original campaign objectives were reduced as Serbian president Slobodan Milošević and his allies gained greater control of the JNA.

The strategic situation permitted the development of the Vance plan—a ceasefire supervised by United Nations peacekeepers designed to create conditions for the political settlement of the conflict in Croatia.

The Yugoslav People's Army (Jugoslovenska Narodna Armija – JNA) confiscated the weapons of Croatia's Territorial Defence (Teritorijalna obrana – TO) to minimize potential resistance.

[2] On 17 August, the tensions escalated into an open revolt by Croatian Serbs,[3] centred on the predominantly Serb-populated areas of the Dalmatian hinterland around Knin,[4] parts of the Lika, Kordun, Banovina regions and eastern Croatia.

[6] After a bloodless skirmish between Serb Krajina Militia and Croatian special police in March,[7] the JNA, supported by Serbia and its allies, asked the federal Presidency to grant it wartime powers and declare a state of emergency.

The request was denied on 15 March,[8] and by the summer of 1991, the JNA came under the control of the Serbian President Slobodan Milošević as the Yugoslav federation started to fall apart.

[10] Milošević, preferring a campaign aimed at expanding Serbia rather than preserving Yugoslavia, publicly threatened to replace the JNA with a Serbian army and declared that he no longer recognized the authority of the federal presidency.

The initial plan of Croatian President Franjo Tuđman was to win support for Croatia from the European Community (EC) and the United States, and he dismissed advice to seize JNA barracks and storage facilities in the country.

In western Slavonia, the Croatian Serb militia attempted to advance into Daruvar but were held back by the ZNG in the area around Okučani and south of Pakrac before the JNA formed a buffer zone there.

[25] The ZNG blockaded 33 large JNA garrisons in Croatia,[26] and numerous smaller facilities including border posts and weapons and ammunition storage depots.

[13] The Battle of the Barracks resulted in a large increase to ZNG weapon holdings—allowing full arming of its existing units, raising of an additional 40–42 brigades and fielding a total of 200,000 troops and 40,000 police by the end of the year.

The first wave of call-ups was performed in July, and was meant to intimidate Croatia without an actual offensive being launched and allow timely deployment of crucial units.

The plan entailed five corps-level campaigns designed to impose an air and naval blockade of Croatia, capture territory populated by Serbs and relieve barracks under ZNG siege.

The southern operational group of the thrust, spearheaded by the 1st Guards Mechanised Division, was expected to lift the ZNG siege of the JNA barracks in Vinkovci, and reach Našice and Slavonski Brod in two to three days.

Besides the bridging units, the division did not receive the 80th Motorised Brigade—which appears to have disintegrated before reaching the Croatian frontier—and the 2nd Guards Mechanised Brigade—a victim of friendly fire bombardment in the area between Tovarnik and Ilača adjacent to the border.

[44][48] The reduced objectives called for offensive and defensive actions, the inflicting of decisive defeats on Croatian forces in Dalmatia and eastern Slavonia, and strikes against vital infrastructure in Croatia, to obtain an agreement on the evacuation of besieged JNA facilities.

[32][51] The JNA effort to relieve its Vukovar barracks turned into a protracted siege, delaying 36,000 troops and a significant proportion of armoured units slated for the thrust towards Zagreb and Varaždin.

[55] In Banovina, the JNA reached the Kupa River and captured its entire southern bank, except for ZNG bridgeheads in the areas of Nebojan, Sunja and Sisak, on 30 September.

[56] The greatest flare-up of hostilities in the area occurred on 4–5 November when a JNA garrison based in a suburb of Karlovac broke through the ZNG siege in the Battle of Logorište and reached JNA-held territory to the east of the city.

[60] In northern Dalmatia, the JNA Knin Corps attacked Zadar on 4 October, reaching its outskirts and lifting the ZNG siege of the Šepurine Barracks the next day.

[56] Further south, the JNA Titograd Corps and its Military-Maritime District forces advanced from eastern Herzegovina and the Bay of Kotor, and pushed east and west of Dubrovnik on 1 October, placing besieging the city by the end of the month.

[67] Even though the declaration had been preceded the day before by a Yugoslav Air Force attack on the presidential office in Zagreb,[68] the Croatian authorities considered that the war situation was no longer critical.

[70] The most significant results were produced in western Slavonia, where Croatian forces began pushing the JNA away from Grubišno Polje towards Lipik on 31 October, and away from Nova Gradiška towards Okučani on 12 November.

Real progress toward ending the fighting came only after the Serbian political leaders concluded that their war aims of achieving military control over Serb areas in Croatia had been fulfilled.

[74] Even though JNA positions in western Slavonia were on the brink of military collapse,[72] the HV struggled elsewhere and its munitions stockpiles were depleted, while the UN arms embargo prevented its quick resupply.

The camps were set up in Begejci, Stajićevo, Sremska Mitrovica, Niš, Aleksinac, Manjača, Banja Luka, Knin, Bučje, Beli Manastir, Negoslavci, Vukovar and Morinj.

The mission was subsequently authorised through United Nations Security Council Resolution 721 of 27 November,[88] following a formal request for the deployment of UN peacekeepers submitted by the Yugoslav government the previous day.

[90] The Implementation Agreement, ensuring the ceasefire required for the deployment of peacekeepers, was signed by Croatian Defence Minister Gojko Šušak and deputy commander of JNA 5th Military District General Andrija Rašeta in Sarajevo, Bosnia and Herzegovina, on 2 January.

The ceasefire generally held after it took effect on 3 January at 6 pm,[91][92] except in the Dubrovnik area,[93] where the JNA remained in positions around the town and in Konavle until July 1992.