In the First multi-party election in Bosnia and Herzegovina, in November 1990, votes were cast largely according to ethnicity, leading to the success of the Bosniak Party of Democratic Action, the Serbian Democratic Party and the Croatian Democratic Union.

On 25 March, Franjo Tuđman and Serbian President Slobodan Milošević held a meeting in Karađorđevo. The meeting became controversial in later months due to claims by some Yugoslav politicians that the two presidents agreed to the partition of Bosnia and Herzegovina.

On 6 June, Izetbegović and Macedonian president Kiro Gligorov proposed a weak confederation between Croatia, Slovenia and a federation of the other four republics, which was rejected by Milošević.

On 25 June 1991, both Slovenia and Croatia declared independence, which led to a short armed conflict in Slovenia called the Ten-Day War, and an all-out war in Croatia in the Croatian War of Independence in areas with a substantial ethnic Serb population.

In July 1991, representatives of the Serb Democratic Party (SDS), including SDS president Karadžić, and Muhamed Filipović and Adil Zulfikarpašić from the Muslim Bosniak Organisation (MBO), drafted an agreement known as the Zulfikarpašić–Karadžić agreement which would leave SR Bosnia and Herzegovina in a state union with SR Serbia and SR Montenegro. The agreement was denounced by Croat political parties. Although initially welcoming the initiative, Izetbegović later dismissed the agreement.

In August 1991, the European Economic Community hosted a conference in an attempt to prevent Bosnia and Herzegovina sliding into war.

In September 1991, Croatian National Guard (ZNG) organised armed incursions across the Croatian border into Bosnia. ZNG opened mortar fire on Bosanska Dubica on 13 September 1991, and raided Bosanski Brod on 15 September 1991.

On 19 September 1991, the JNA moved extra troops to the area around the city of Mostar, which was publicly protested by the local government.

On 20 September 1991, the JNA transferred troops to the front at Vukovar via the Višegrad region of northeastern Bosnia. In response, local Croats and Bosniaks set up barricades and machine-gun posts. They halted a column of 60 JNA tanks but were dispersed by force the following day. More than 1,000 people had to flee the area. This action, nearly seven months before the start of the Bosnian War, caused the first casualties of the Yugoslav Wars in Bosnia.

On 25 September 1991, the United Nations Security Council passed Resolution 713, imposing an arms embargo on all of the former Yugoslav territories. The embargo hurt the Army of Republic of Bosnia and Herzegovina the most because the Republic of Serbia inherited the lion's share of the Yugoslav People Army's arsenal and the Croatian Army could smuggle weapons through its coast. Over 55% of the armories and barracks of the former Yugoslavia were located in Bosnia, owing to its mountainous terrain in anticipation of a guerrilla war had Yugoslavia been invaded, but many of those factories (such as the UNIS PRETIS factory in Vogošća) were under Serb control, and others were inoperable due to a lack of electricity and raw materials.

On 15 October 1991, the parliament of the Socialist Republic of Bosnia and Herzegovina in Sarajevo passed a "Memorandum on the Sovereignty of Bosnia-Herzegovina" by a simple majority.

The Serb political representatives proclaimed the Assembly of the Serb People of Bosnia and Herzegovina on 24 October 1991, declaring that the Serb people wished to remain in Yugoslavia.

On 12 November 1991, the Croatian Community of Bosnian Posavina was established in Bosanski Brod. It covered eight municipalities in northern Bosnia.

On 18 November 1991, the Croatian Community of Herzeg-Bosnia was established in Mostar. Mate Boban was chosen as its president. Its founding document said: "The Community will respect the democratically elected government of the Republic of Bosnia and Herzegovina for as long as exists the state independence of Bosnia and Herzegovina in relation to the former, or any other, Yugoslavia".

On 9 January 1992, the Bosnian Serbs proclaimed the "Republic of the Serbian People in Bosnia-Herzegovina" (SR BiH, later Republika Srpska), but did not officially declare independence.

The Arbitration Commission of the Peace Conference on Yugoslavia in its 11 January 1992 Opinion No. 4 on Bosnia and Herzegovina stated that the independence of Bosnia and Herzegovina should not be recognised because the country had not yet held a referendum on independence.

There is debate over the start date of the Bosnian War. Clashes between Bosnian Muslims, Serbs and Croats started in late February 1992.

The Croatian War would result in United Nations Security Council Resolution 743 on 21 February 1992, which created the United Nations Protection Force (UNPROFOR).

The Bosnian Serb assembly members advised Serbs to boycott the referendums held on 29 February and 1 March 1992. The turnout to the referendums was reported as 63.7%, with 92.7% of voters voting in favour of independence (implying that Bosnian Serbs, which made up approximately 34% of the population, largely boycotted the referendum).

Serbs consider the Sarajevo wedding shooting, when a groom's father was killed on the second day of the Bosnian independence referendum, 1 March 1992, to have been the first victim of the war.

The Serb political leadership used the referendum as a pretext to set up roadblocks in protest. Independence was formally declared by the Bosnian parliament on 3 March 1992.

On 18 March 1992, all three sides signed the Lisbon Agreement: Alija Izetbegović for the Bosniaks, Radovan Karadžić for the Serbs and Mate Boban for the Croats.

The Sijekovac killings of Serbs took place on 26 March.

on 28 March 1992, Izetbegović, after meeting with the then-US ambassador to Yugoslavia Warren Zimmermann in Sarajevo, withdrew his signature and declared his opposition to any type of ethnic division of Bosnia.

The war in Bosnia escalated in April.

The Bijeljina Killings (of mostly Bosniaks) on 1–2 April.

On 3 April, the Battle of Kupres began between the JNA and a combined HV-HVO force that ended in a JNA victory.

"full-scale hostilities had broken out by 6 April", the same day that the United States and European Economic Community (EEC) recognized Bosnia and Herzegovina.

On 6 April Serb forces began shelling Sarajevo, and in the next two days crossed the Drina from Serbia proper and besieged Muslim-majority Zvornik, Višegrad and Foča.

On 23 April, the JNA evacuated its personnel by helicopters from the barracks in Čapljina, which was under blockade since 4 March.

On 27 April, the Bosnian government ordered the JNA to be put under civilian control or expelled, which was followed by a series of conflicts in early May between the two.

Prijedor was taken over by Serbs on 30 April.

From May to December 1992, the Bosnian Ministry of the Interior (BiH MUP), Croatian Defence Council (HVO) and later the Bosnian Territorial Defence Forces (TO RBiH) operated the Čelebići prison camp. It was used to detain 700 Bosnian Serb prisoners of war arrested during military operations that were intended to de-block routes to Sarajevo and Mostar in May 1992 which had earlier been blocked by Serb forces. Of these 700 prisoners, 13 died while in captivity.

On 2 May, the Green Berets and local gang members fought back a disorganized Serb attack aimed at cutting Sarajevo in two.

On May 3, Izetbegović was kidnapped at the Sarajevo airport by JNA officers, and used to gain safe passage of JNA troops from downtown Sarajevo.

On 6 May 1992, Mate Boban met with Radovan Karadžić in Graz, Austria, where they reached an agreement for a ceasefire and discussed the details of the demarcation between a Croat and Serb territorial unit in Bosnia and Herzegovina.

The Army of Republika Srpska (Vojska Republike Srpske, VRS) was established on 12 May 1992. It was loyal to Republika Srpska, a Serb breakaway state that sought unification with FR Yugoslavia.

On 15 May 1992, a JNA column was ambushed in Tuzla. 92nd Motorised JNA Brigade (stationed in "Husinska buna" barracks in Tuzla) received orders to leave the city of Tuzla and Bosnia-Herzegovina, and to enter Serbia.

The Republic of Bosnia and Herzegovina was admitted as a member State of the United Nations on 22 May 1992.

The Army of Republika Srpska was newly established and put under the command of General Ratko Mladić, in a new phase of the war. Shelling on Sarajevo on 24, 26, 28 and 29 May were attributed to Mladić by UN Secretary-General Boutros Boutros-Ghali.

By June 1992, the number of refugees and internally displaced persons had reached 2.6 million.

An armed conflict occurred in Busovača in early May and another one on 13 June.

In June 1992, the Bosnian Serbs started Operation Vrbas 92.

On 5 and 6 June the last JNA personnel left the city during heavy street fighting and shelling.

On 19 June, a conflict between the units of the TO on one side, and HVO and HOS units on the other side broke out in Novi Travnik.

The 20 June cease-fire, executed in order for UN takeover of the Sarajevo airport for humanitarian flights, was broken as both sides battled for control of the territory between the city and airport.

On 21 June 1992, Bosniak forces entered the Bosnian Serb village of Ratkovići near Srebrenica and murdered 24 Serb civilians.

In June 1992, the Bosnian Serbs started Operation Corridor 92.

The airport crisis led to Boutros-Ghali's ultimatum on 26 June, that the Serbs stop attacks on the city, allow the UN to take control of the airport, and place their heavy weapons under UN supervision.

On 21 July 1992, the Agreement on Friendship and Cooperation was signed by Tuđman and Izetbegović, establishing a military cooperation between the two armies.

On 12 August 1992, the name of the Serbian Republic of Bosnia and Herzegovina was changed to Republika Srpska (RS).

By September 1992, Croatia had accepted 335,985 refugees from Bosnia and Herzegovina, mostly Bosniak civilians (excluding men of drafting age).

Numerous peace plans were proposed by the UN, the United States, and the European Community (EC), but with little impact on the war. The most notable proposal was the Vance-Owen Peace Plan, revealed in January 1993.

On 7 January 1993, Orthodox Christmas Day, 8th Operational Unit Srebrenica, a unit of the ARBiH under the command of Bratunac Killings, attacked the village of Kravica near Bratunac. 46 Serbs died in the attack: 35 soldiers and 11 civilians.

On 8 January 1993, the Serbs killed the deputy prime minister of the ARBiH Hakija Turajlić after stopping the UN convoy taking him from the airport.

On 16 January 1993, soldiers of the ARBiH attacked the Bosnian Serb village of Skelani, near Srebrenica. 69 people were killed, 185 were wounded. Among the victims were 6 children.

By 26 January, the ARBiH seized control of several villages in the area, including Kaćuni and Bilalovac on the Busovača–Kiseljak road, thus isolating Kiseljak from Busovača. In the Kiseljak area, the ARBiH secured the villages northeast of the town of Kiseljak, but most of the municipality and the town itself remained in HVO control.

On 30 January, ARBiH and HVO leaders met in Vitez, together with representatives from UNPROFOR and other foreign observers, and signed a ceasefire in the area of central Bosnia, which came into effect on the following day.

On 22 February 1993, the United Nations Security Council passed Resolution 808 that decided "that an international tribunal shall be established for the prosecution of persons responsible for serious violations of international humanitarian law".

On 31 March 1993, the United Nations Security Council issued Resolution 816, calling on member states to enforce a no-fly zone over Bosnia-Herzegovina.

On 12 April 1993, NATO commenced Operation Deny Flight to enforce this no-fly zone.

The April incidents escalated into an armed conflict on 15 April in the area of Vitez, Busovača, Kiseljak and Zenica. The outnumbered HVO in the Zenica municipality was quickly defeated, followed by a large exodus of Croat civilians.

On 16 April, 15 Croat civilians and 7 POWs were killed by the ARBiH in the village of Trusina, north of Jablanica.

On 16 April, the HVO (The Croatian Defence Council) launched a spoiling attack on the village of Ahmići, east of Vitez. After the attacking units breached the ARBiH lines and entered the village, groups of irregular HVO units went from house to house, burning them and killing civilians.

On 24 April, mujahideen forces attacked the village of Miletići northeast of Travnik and killed four Croat civilians. The rest of the captured civilians were taken to the Poljanice camp.

On 25 April, Izetbegović and Boban signed a ceasefire agreement.

On 15–16 May, the Vance-Owen peace plan was rejected on a referendum.

On 25 May 1993 the International Criminal Tribunal for the former Yugoslavia (ICTY) was formally established by Resolution 827 of the United Nations Security Council.

On 4 June 1993, the UN Security Council passed Resolution 836 authorising the use of force by UNPROFOR in the protection of the safe zones.

On 8 June, 24 Croat civilians and POWs were killed by the mujahideen near the village of Bikoši.

A similar development took place in Novi Travnik. On 9 June, the ARBiH (Army of the Republic of Bosnia and Herzegovina) attacked HVO units positioned east of the town, facing the VRS in Donji Vakuf, and the next day heavy fighting followed in Novi Travnik.

The ARBiH offensive continued east of Travnik to secure the road to Zenica, which was achieved by 14 June.

By 15 June, the ARBiH secured the area northwest of the town, while the HVO kept the northeastern part of the municipality and the town of Novi Travnik. The battle continued into July with only minor changes on the front lines.

On 15 June 1993, Operation Sharp Guard, a naval blockade in the Adriatic Sea by NATO and the Western European Union, began and continued until it was lifted on 18 June 1996 on termination of the UN arms embargo.

On 24 June, the Battle of Žepče began that ended with an ARBiH defeat on 30 June.

In the Kiseljak enclave, the HVO held off an attack on Kreševo, but lost Fojnica on 3 July.

At the beginning of September, the ARBiH launched an operation known as Operation Neretva 93 against the HVO in Herzegovina and central Bosnia, on a 200 km long front. It was one of their largest offensives in 1993.

During the night of 8/9 September, at least 13 Croat civilians were killed by the ARBiH in the Grabovica Killings.

29 Croat civilians were killed in the Uzdol Killings on 14 September.

On 23 October, 37 Bosniaks were killed by the HVO in the Stupni Do massacre.

On 5 February 1994, Sarajevo suffered its deadliest single attack of the entire siege with the first Markale massacre, when a 120 millimeter mortar shell landed in the centre of the crowded marketplace, killing 68 people and wounding another 144.

On 6 February, UN Secretary-General Boutros Boutros-Ghali formally requested NATO to confirm that future requests for air strikes would be carried out immediately.

On 9 February 1994, NATO authorized the Commander of Allied Forces Southern Europe (CINCSOUTH), US Admiral Jeremy Boorda, to launch air strikes—at the request of the UN—against artillery and mortar positions in or around Sarajevo determined by UNPROFOR to be responsible for attacks against civilian targets.

On 12 February, Sarajevo enjoyed its first casualty free day since April 1992.

The large-scale removal of Bosnian-Serb heavy weapons began on 17 February 1994.

NATO also issued an ultimatum to the Bosnian Serbs demanding the removal of heavy weapons around Sarajevo by midnight of 20–21 February, or they would face air strikes.

The Croat-Bosniak war ended with the signing of a ceasefire agreement between the HVO Chief of Staff, general Ante Roso, and the ARBiH Chief of Staff, general Rasim Delić, on 23 February 1994 in Zagreb. The agreement went into effect on 25 February.

NATO became actively involved when its jets shot down four Serb aircraft over central Bosnia on 28 February 1994 for violating the UN no-fly zone.

On 12 March 1994, the United Nations Protection Force (UNPROFOR) made its first request for NATO air support, but close air support was not deployed, owing to a number of delays associated with the approval process.

A peace agreement known as the Washington Agreement, mediated by the US, was concluded on 2 March by representatives of the Republic of Bosnia and Herzegovina, Croatia and Herzeg-Bosnia.

On 20 March an aid convoy with medical supplies and doctors reached Maglaj, a city of 100,000 people, which had been under siege since May 1993 and had been surviving off food supplies dropped by US aircraft. A second convoy on 23 March was hijacked and looted.

On 10–11 April 1994, UNPROFOR called in air strikes to protect the Goražde safe area, resulting in the bombing of a Serbian military command outpost near Goražde by two US F-16 jets.

In retaliation, Serbs took 150 U.N. personnel hostage on 14 April.

On 15 April, the Bosnian government lines around Goražde broke.

Around 29 April 1994, a Danish contingent (Nordbat 2) on peacekeeping duty in Bosnia, as part of UNPROFOR's Nordic battalion located in Tuzla, was ambushed when trying to relieve a Swedish observation post (Tango 2) that was under heavy artillery fire by the Bosnian Serb Šekovići brigade at the village of Kalesija.

On 12 May, the US Senate adopted S. 2042, introduced by Sen. Bob Dole, to unilaterally lift the arms embargo against the Bosnians, but it was repudiated by President Clinton.

On 5 August, at the request of UNPROFOR, NATO aircraft attacked a target within the Sarajevo Exclusion Zone after weapons were seized by Bosnian Serbs from a weapons collection site near Sarajevo.

On 22 September 1994, NATO aircraft carried out an air strike against a Bosnian Serb tank at the request of UNPROFOR.

On 5 October 1994, Pub.L. 103–337 was signed by the President and stated that if the Bosnian Serbs had not accepted the Contact Group proposal by 15 October the President should introduce a UN Security Council proposal to end the arms embargo, and that if it was not passed by 15 November, only funds required by all UN members under Resolution 713 could be used to enforce the embargo, which would effectively end the embargo.

Operation Amanda was an UNPROFOR mission led by Danish peacekeeping troops, with the aim of recovering an observation post near Gradačac, Bosnia and Herzegovina, on 25 October 1994.

The first military effort coordinated between the HVO and the ARBiH following the Washington Agreement was the advance towards Kupres, which was retaken from the VRS on 3 November 1994.

On 12–13 November, the US unilaterally lifted the arms embargo against the government of Bosnia.

On 19 November 1994, the North Atlantic Council approved the extension of Close Air Support to Croatia for the protection of UN forces in that country.

NATO aircraft attacked the Udbina airfield in Serb-held Croatia on 21 November, in response to attacks launched from that airfield against targets in the Bihac area of Bosnia and Herzegovina.

On 29 November, the HV and the HVO initiated Operation Winter 94 in southwestern Bosnia. After a month of fighting, Croat forces had taken around 200 square kilometres (77 square miles) of VRS-held territory and directly threatened the main supply route between Republika Srpska and Knin, the capital of Republic of Serbian Krajina. The primary objective of relieving pressure on the Bihać pocket was not achieved, although the ARBiH repelled VRS attacks on the enclave.

On 25 May 1995, NATO bombed VRS positions in Pale due to their failure to return heavy weapons.

On 11 July 1995, Army of Republika Srpska (VRS) forces under general Ratko Mladić occupied the UN "safe area" of Srebrenica in eastern Bosnia.

the Split Agreement signed between Tuđman and Izetbegović on 22 July.

Military offensive by the HV (the Croatian Army) and the HVO (the Croatian Defence Council) codenamed Operation Summer 95 took place in western Bosnia.

On 4 August, the HV (the Croatian Army) launched Operation Storm that effectively dissolved the Republic of Serbian Krajina.

On 28 August, a VRS mortar attack on the Sarajevo Markale marketplace killed 43 people.

The Secretary General of NATO announced the start of Operation Deliberate Force, widespread airstrikes against Bosnian Serb positions supported by UNPROFOR rapid reaction force artillery attacks.

The HV-HVO secured over 2,500 square kilometers (970 square miles) of territory during Operation Mistral 2, including the towns of Jajce, Šipovo and Drvar.

At the same time, the ARBiH engaged the VRS further to the north in Operation Sana and captured several towns, including Bosanska Krupa, Bosanski Petrovac, Ključ and Sanski Most.

On 14 September 1995, the NATO air strikes were suspended to allow the implementation of an agreement with Bosnian Serbs for the withdrawal of heavy weapons from around Sarajevo.

Operation Una, began on 18 September 1995, when HV crossed the Una river and entered Bosnia.

Twelve days later, on 26 September, an agreement of further basic principles for a peace accord was reached in New York City between the foreign ministers of Bosnia and Herzegovina, Croatia and the FRY.

The ARBiH requested Croatian assistance and on 8 October the HV-HVO launched Operation Southern Move under the overall command of HV Major General Ante Gotovina. The VRS lost the town of Mrkonjić Grad, while HVO units came within 25 kilometres (16 miles) south of Banja Luka.

A 60-day ceasefire came into effect on 12 October.

On 1 November, peace talks began in Dayton, Ohio.

The war ended with the Dayton Peace Agreement signed on 21 November 1995.

The war was brought to an end by the General Framework Agreement for Peace in Bosnia and Herzegovina, negotiated at Wright-Patterson Air Force Base in Dayton, Ohio between 1 and 21 November 1995 and signed in Paris on 14 December 1995.