It was launched from the area of Bihać on 13 September 1995, against the Army of Republika Srpska (Vojska Republike Srpske – VRS), and involved advances towards Bosanski Petrovac, Sanski Most and Bosanska Krupa.

Operation Sana, alongside concurrent HV and HVO offensives, sparked debate among military analysts as to whether the ground assaults or NATO's airstrikes were more responsible for ending the Bosnian War.

In the final days of March, Bosnian Serb forces bombarded Bosanski Brod with artillery, resulting in a cross-border operation by the Croatian Army (Hrvatska vojska – HV) 108th Brigade.

[4] The JNA and the VRS in Bosnia and Herzegovina faced the Army of the Republic of Bosnia and Herzegovina (Armija Republike Bosne i Hercegovine – ARBiH) and the Croatian Defence Council (Hrvatsko vijeće obrane – HVO), reporting to the Bosniak-dominated central government and the Bosnian Croat leadership respectively, as well as the HV, which occasionally supported HVO operations.

[9] By 1995, the ARBiH and the HVO had developed into better-organised forces employing comparably large numbers of artillery pieces and good defensive fortifications.

[10] In August 1995, after the fall of most of the Croatian Serb-controlled areas of Croatia during Operation Storm, the HV shifted its focus to western Bosnia.

The shift was motivated by the desire to create a security zone along the Croatian border, establish Croatia as a regional power and gain favours with the West by forcing an end to the Bosnian War.

[11] In the final days of August 1995, NATO launched an air campaign targeting the VRS, codenamed Operation Deliberate Force.

[18] The 15,000-strong ARBiH 5th Corps, commanded by Divisional General Atif Dudaković, was assigned the primary objectives, the capture of Bosanska Krupa, Bosanski Petrovac, Ključ and Sanski Most.

As its defences yielded to the ground assault supported by HV artillery fire, the VRS started to retreat south towards Bosanski Petrovac, alongside civilians fleeing the area.

An effort to widen the salient commenced on 15 September, when OG North moved against Bosanska Krupa and Otoka in an assault spearheaded by the 503rd, 505th and 517th brigades.

The latter included the Serb Volunteer Guard (Srpska dobrovoljačka garda – SDG),[24] led by Željko Ražnatović Arkan,[25] and Serbia's State Security Service Red Berets.

The HV managed to establish several small bridgeheads on the right bank of the river, but the operation was called off after two days of fighting due to high casualties brought on by poor planning.

[24] On 22 September, Colonel General Ratko Mladić cut short his medical treatment in Belgrade to return to Banja Luka and control the VRS more directly.

[27] The counteroffensive commenced on the night of 23/24 September, with the VRS 65th Protection Regiment, 16th Krajina and 43rd Motorised brigades and SDG troops attacking OG North.

In this operation, the HV and the HVO fielded 11,000–12,000 troops who captured Mrkonjić Grad from three VRS brigades, thus relieving the pressure on the ARBiH in Ključ.

On 10 October, elements of the VRS 43rd Motorised and 11th Dubica brigades launched an unsuccessful attempt to halt the ARBiH advance on the outskirts of Sanski Most.

[35] Despite the fact that a ceasefire was scheduled to come into force throughout Bosnia and Herzegovina on 12 October, OG Centre continued its advance northeast of Sanski Most, engaging the bulk of the VRS 43rd Motorised Brigade in a series of clashes.

[33] A Central Intelligence Agency analysis comparing the effects of Operation Deliberate Force, Sana and Maestral 2 on the VRS noted that the NATO campaign did not degrade the combat capability of the VRS as much as was initially assumed, because the airstrikes were never primarily directed at field-deployed units, rather they targeted the command and control infrastructure of the Bosnian Serb military.

The analysis concluded that, while NATO degraded the capabilities of the VRS, the final HV, HVO and ARBiH offensives inflicted the most damage.

[37] Author Robert C. Owen argues that the HV, HVO and ARBiH would not have advanced as rapidly as they did had NATO not intervened and denied the VRS its long-range communications.

According to British historian Marko Attila Hoare, their acquiescence was secured following massive diplomatic pressure from the West, and the alleged threat of US airstrikes against the ARBiH if it breached the ceasefire.

[40] In September and October, 6,500 Bosniak and Croat civilians living in the area of Banja Luka or Prijedor were expelled from their homes by Bosnian Serb forces.

Changes of control of territory also allowed access to two mass graves near Sanski Most, believed to contain the bodies of 300 civilians killed by Bosnian Serb forces in April 1992.