The attacking force of 8,500 troops commanded by HV's Lieutenant General Ante Gotovina initially encountered strong resistance from the 5,500-strong Army of Republika Srpska (VRS) 2nd Krajina Corps.

Operation Summer '95 was launched in response to the resumption of attacks by the VRS and the RSK military on the Bihać pocket—one of six United Nations Safe Areas established in Bosnia and Herzegovina.

The international community feared the worst humanitarian disaster of the war to that point would occur if the RSK or the VRS overran the Bihać pocket.

[15] After a series of unsuccessful ceasefires, the United Nations Protection Force (UNPROFOR) was deployed to Croatia to supervise and maintain the agreement.

[15] Serbia continued to support the RSK,[17] but a series of HV advances restored small areas to Croatian control as the siege of Dubrovnik was lifted,[18] and Operation Maslenica resulted in minor tactical gains.

[19] In response to the HV successes, the RSK intermittently attacked a number of Croatian towns and villages with artillery and missiles.

In the final days of March, the Bosnian Serb army started shelling Bosanski Brod,[23] and Sarajevo was attacked on 4 April.

[25] This was achieved through a large-scale campaign of territorial conquest and ethnic cleansing which was backed by military and financial support from the Federal Republic of Yugoslavia.

[48] Because the UN arms embargo was still in place, the MPRI was hired ostensibly to prepare the HV for participation in the NATO Partnership for Peace programme.

It has also been speculated in several sources,[47]—including The New York Times and various Serbian media reports,[49][50]— that the MPRI may have provided doctrinal advice, scenario planning and US government satellite intelligence to Croatia.

[55] The Washington Agreement also resulted in a series of meetings between Croatian and US government and military officials held in Zagreb and Washington, D.C. On 29 November 1994, the Croatian representatives proposed to attack Serb-held territory from Livno in Bosnia and Herzegovina, to draw off a part of the force besieging Bihać and to prevent its capture by the Serbs.

Besides contributing to the defence of Bihać, the attack shifted the line of contact of the HV and the HVO closer to the RSK's supply routes.

The move provided the HV with a chance to extend their territorial gains from Operation Winter '94 by advancing from the Livno Valley.

[57] The defending force consisted of approximately 5,500 troops drawn from the VRS 2nd Krajina Corps, commanded by Major General Radivoje Tomanić.

[58] The area was additionally reinforced following the HV's Operation Leap 2 in June 1995, using three VRS brigades deployed to Bosansko Grahovo and Glamoč.

The Bosansko Grahovo zone was particularly well prepared for defence—fortifications, shelters and covered trenches were built to establish defence in depth, with obstacles, including minefields, in between them.

The HV 81st Guards Battalion advancing south-east from the Šator Mountain to the rear of Glamoč broke forward the defences of the VRS 3rd Serbian Brigade.

However, it paused its push after less than 2 kilometres (1.2 miles) because its right flank came into jeopardy when the HV and HVO units to their right were held back by the VRS's determined defence.

The HVO 60th Guards Airborne Battalion and the 22nd Sabotage Detachment attacked in Kujača Hill south-east of Glamoč, but they too made only marginal gains.

The Croatian Air Force took part in the attack the same day, using two MiG-21s to conduct airstrikes designed to disrupt the road network around Glamoč, violating a no-fly zone imposed by the UN and enforced by NATO as Operation Deny Flight.

At the same time, the HV 81st Guards Battalion and the 1st HGZ, supported by the special police, moved north of Glamoč, reaching its outskirts and cutting the main route between the town and the rest of the Bosnian Serb-held territory.

[68] VRS Supreme Commander Colonel General Ratko Mladić visited Knin the same day, also promising to restore the territory lost that month.

[74] Operation Summer '95 failed to achieve its goal of relieving Bihać by drawing substantial RSK forces and the VRS away from the city to contain the HV/HVO advance.

The RSK 2nd Guards Brigade was ordered to move from Bihać to Bosansko Grahovo,[62] and it remained in the Knin area until the beginning of the following HV offensive, Operation Storm, on 4 August.

On 30 July, RSK civilian and military leaders, Milan Martić and General Mile Mrkšić, met with a personal representative of Secretary-General of the United Nations Yasushi Akashi and agreed upon a plan to withdraw from Bihać to prevent the expected Croatian offensive.