Una-class submarine

All six boats were in service with the 88th submarine flotilla of the JRM with Lora Naval Base being their homeport. At the start of the Croatian War of Independence all boats except Soča were relocated to Montenegro without participating in combat operations. Croatian forces captured Soča in drydock at the BSO where it was undergoing an overhaul. Soča underwent a modification program that improved its autonomy by installing a diesel generator. It was recommissioned, now with the Croatian Navy, in 1996 as Velebit (P-01) and remained in service until the early 2000s when it was declared redundant. The remaining boats entered service with the new SR Yugoslav Navy. The first ones to be decommissioned sometime between 1997 and 2001 were Tisa and Una. In 2003 a decision was made that the ongoing major overhaul of Kupa would stop; the boat was decommissioned and broken up in 2008. It appears that the last Una-class boats in service with the SR Yugoslav Navy were Zeta and Vardar, both of them being decommissioned in 2005.^[8][16][14]

Ownership of the decommissioned boats passed on to Montenegro after the country declared independence in 2006, ending the state of Serbia and Montenegro and its joint armed forces. In 2009 the Ministry of Defence announced that it is willing to donate three Una-class submarines to former SFR Yugoslav republics of Slovenia, Croatia and Serbia.^[17] Although the "Submariner" society from Pula was interested in accepting the donation and exhibiting it in a museum, the Croatian MoD responded with a statement that accepting the donation is against national interests; since most of the fleet of the former Yugoslav Navy was relocated to Montenegro at the beginning of the Croatian War of Independence, Croatia claims the military equipment of the former joint armed forces was stolen, and should be a subject of succession. The MoD further explains that the state interest is in compensation for that equipment, not returning "obsolete, damaged and corroded equipment which nowadays Serbia and Montenegro are unsuccessfully trying to sell".^[18]

Slovenia on the other hand reacted positively to the offer; in 2011 Zeta was loaded on a truck and transported to Bar, then across Adriatic to Bari, Italy and along Italian coast to Slovenia. Although longer and thus more expensive, sea routes and roads that included crossing the Croatian border were avoided in fear of Croatian authorities confiscating the submarine.^[12] P-913 was restored with the help of the "Slovenian Submariners Society" and the Slovenian Army, being officially placed on display at the Pivka Park of Military History on 17 September 2011.^[19]

In 2013, Una and a Heroj-class attack submarine, Heroj (P-821), were restored and opened to the public in the museum section of the Porto Montenegro marina. The project was initiated by the "Submariner" Society from Tivat and was, after approval by the Montenegro MoD, financed by Porto Montenegro.^[20][11] The donation of one of the submarines to Serbia was initiated by the "Submariner" society from Belgrade in 2009. However it wasn't until five years later in June 2014 that the Government of Montenegro officially accepted the proposal and agreed to cede Tisa (P-911) to Serbia. The submarine will be exhibited at the Museum of Science and Technology in Belgrade.^[9]