The Croatian Republic of Herzeg-Bosnia (Croatian: Hrvatska Republika Herceg-Bosna) was an unrecognized geopolitical entity and quasi-state in Bosnia and Herzegovina. It was proclaimed on 18 November 1991 under the name Croatian Community of Herzeg-Bosnia (Croatian: Hrvatska Zajednica Herceg-Bosna) as a "political, cultural, economic and territorial whole" in the territory of Bosnia and Herzegovina, and abolished on 14 August 1996.
The Croatian Community of Bosnian Posavina, proclaimed in northern Bosnia on 12 November 1991, was joined with Herzeg-Bosnia in October 1992. In its proclaimed borders, Herzeg-Bosnia encompassed about 30% of the country, but did not have effective control over the entire territory as parts of it were lost to the Army of Republika Srpska (VRS) at the beginning of the Bosnian War. The armed forces of Herzeg-Bosnia, the Croatian Defence Council (HVO), were formed on 8 April 1992 and initially fought in an alliance with the Army of the Republic of Bosnia and Herzegovina. Their relations deteriorated throughout late 1992, which led to the Croat–Bosniak War.
The Constitutional Court of the Republic of Bosnia and Herzegovina declared Herzeg-Bosnia unconstitutional on 14 September 1992. Herzeg-Bosnia formally recognized the Government of the Republic of Bosnia and Herzegovina and functioned as a state within a state, while some in its leadership advocated the secession of the entity and its unification with Croatia.
On 28 August 1993, Herzeg-Bosnia was declared a republic following the proposal of the Owen-Stoltenberg Plan, envisioning Bosnia and Herzegovina as a union of three republics. Its capital city was Mostar, which was then a war zone, and the effective control center was in Grude. In March 1994, the Washington Agreement was signed that ended the conflict between Croats and Bosniaks. Under the agreement, Herzeg-Bosnia was to be joined with Bosniaks into the Federation of Bosnia and Herzegovina, but it continued to exist until it was formally abolished in 1996.
The Hague Tribunal ruled that Herceg-Bosna served as a means for pursuing a joint criminal enterprise whose aim was to create a Croatian entity in Bosnia and Herzegovina, one with an overwhelming Croat majority, and to ultimately annex that entity to the Republic of Croatia. This involved the leadership and authorities of Herceg-Bosna, the Croatian Defence Council, the HDZ and HDZ BiH, as well as members of various Croatian armed forces and intelligence services. Members of the wartime leadership of Herceg-Bosna were indicted or convicted before the ICTY for the gravest crimes under international law, including ethnic cleansing, crimes against humanity, and war crimes committed against Bosnian Muslims and Serbs.
The term Herzeg-Bosnia (Croatian: Herceg-Bosna) appeared in the late 19th century and was used as a synonym for Bosnia and Herzegovina without political connotations. It was often found in folk poems as a more poetic name for Bosnia and Herzegovina. One of the earliest mentions of the term was by Croatian writer Ivan Zovko in his 1899 book Croatianhood in the Tradition and Customs of Herzeg-Bosnia. Croatian historian Ferdo Šišić used the term in his 1908 book Herzeg-Bosnia on the Occasion of Annexation. In the first half of the 20th century the name Herzeg-Bosnia was used by historians such as Hamdija Kreševljaković and Dominik Mandić and Croatian politicians Vladko Maček and Mladen Lorković. Its usage decreased in the second half of the 20th century until 1991 and the proclamation of the Croatian Community of Herzeg-Bosnia. Since the 1990s, it has been used as a name for a Croat territorial unit in Bosnia and Herzegovina.
After the Washington Agreement was signed in March 1994 and the Federation of Bosnia and Herzegovina was created, one of its cantons was named the Herzeg-Bosnia Canton. In 1997, that name was declared unconstitutional by the Constitutional Court of the Federation of Bosnia and Herzegovina, and officially renamed Canton 10.
In early 1991, following the 14th Extraordinary Congress of the Communist Party of Yugoslavia, the leaders of the six Yugoslav republics began a series of meetings to solve the crisis in Yugoslavia. The Serbian leadership favored the centralisation of the country, whereas the Croatian and Slovenian leadership favored a confederation of sovereign states or federalization. Alija Izetbegović proposed an asymmetrical federation on 22 February, where Slovenia and Croatia would maintain loose ties with the four remaining republics. Shortly after that, he changed his position and opted for a sovereign Bosnia and Herzegovina as a prerequisite for such a federation. On 25 March 1991, Croatian president Franjo Tuđman met with Serbian president Slobodan Milošević in Karađorđevo, allegedly to discuss 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 13 July, the government of Netherlands, then the presiding EC country, suggested to other EC countries that the possibility of agreed changes to Yugoslav Republics borders could be explored, but the proposal was rejected by other members. In July 1991, Radovan Karadžić, president of the self-proclaimed Republika Srpska, and Muhamed Filipović, vice president of the Muslim Bosniak Organisation (MBO), drafted an agreement between the Serbs and Bosniaks which would leave Bosnia in a state union with SR Serbia and SR Montenegro. The Croatian Democratic Union (HDZ BiH) and the Social Democratic Party (SDP BiH) denounced the agreement, calling it an anti-Croat pact and a betrayal. Although initially welcoming the initiative, Izetbegović also dismissed the agreement.
From July 1991 to January 1992, during the Croatian War of Independence, the Yugoslav People's Army (JNA) and Serb paramilitaries used Bosnian territory to wage attacks on Croatia. The Croatian government helped arm the Croats and Bosniaks in Bosnia and Herzegovina, expecting the war to spread there. By late 1991 about 20,000 Croats in Bosnia and Herzegovina, mostly from the Herzegovina region, enlisted in the Croatian National Guard. During the war in Croatia, Bosnian president Izetbegović gave a televised proclamation of neutrality, stating that "this is not our war", and the Sarajevo government was not taking defensive measures against a probable attack by the Bosnian Serbs and the JNA. Izetbegović agreed to disarm the existing Territorial Defense (TO) forces on the demand of the JNA. This was defied by Bosnian Croats and Bosniak organizations that gained control of many facilities and weapons of the TO.
In October 1991 the Croat village of Ravno in Herzegovina was attacked and destroyed by JNA forces before turning south towards the besieged Dubrovnik. These were the first Croat casualties in Bosnia and Herzegovina. Izetbegović did not react to the attack on Ravno. The leadership of Bosnia and Herzegovina initially showed a willingness to remain in a rump Yugoslavia but later advocated for a unified Bosnia and Herzegovina.
On 12 November 1991, at a meeting chaired by Dario Kordić and Mate Boban, local party leaders of the HDZ BiH reached an agreement to undertake a policy of achieving an "age-old dream, a common Croatian State" and decided that the proclamation of a Croatian banovina in Bosnia and Herzegovina should be the "initial phase leading towards the final solution of the Croatian question and the creation of a sovereign Croatia within its ethnic and historical [...] borders." On the same day, the Croatian Community of Bosnian Posavina was proclaimed in municipalities of northwest Bosnia in Bosanski Brod.
On 18 November, the autonomous Croatian Community of Herzeg-Bosnia (HZ-HB) was established, it claimed it had no secession goal and that it would serve a "legal basis for local self-administration". The decision on its establishment stated that 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". Boban was established as its president. One of Boban's advisers stated that Herzeg-Bosnia was only a temporary measure and that the entire area would in the end be an integral part of Bosnia and Herzegovina. From its inception the leadership of Herzeg-Bosnia and Croatian Defence Council (HVO) held close relations to the Croatian government and the Croatian Army (HV). At a session of the Supreme State Council of Croatia, Tuđman said that the establishment of Herzeg-Bosnia was not a decision to separate from Bosnia and Herzegovina. On 23 November, the Bosnian government declared Herzeg-Bosnia unlawful.