'Knight's move') was a combined airborne and ground assault by the German XV Mountain Corps and collaborationist forces on the Supreme Headquarters of the Yugoslav Partisans in the Bosnian town of Drvar in the Independent State of Croatia during World War II.

It was launched 25 May 1944, with the goal of capturing or killing Partisan leader Marshal Josip Broz Tito and destroying the headquarters, support facilities and co-located Allied military missions.

On 6 April 1941 the Axis powers invaded Yugoslavia from multiple directions, rapidly overwhelming the under-prepared Royal Yugoslav Army which capitulated 11 days later.

It appears that he did not pass on the useful intelligence he had gathered to SS-Hauptsturmführer[d] Kurt Rybka, the commander of the 500th SS Parachute Battalion, who was responsible for planning the critical airborne aspects of the operation.

[19] Largely due to interservice rivalry and competition,[16] the three organisations did not share the intelligence they gathered, which had a significant effect on the tactical planning and execution of the operation.

They may have become aware of the isolation of the 500th SS Parachute Battalion or the concentration of transport aircraft and gliders at Zagreb and Banja Luka over a month before the operation.

As a result of these early indicators of an attack, Tito's main headquarters was relocated to another cave near the village of Bastasi, 7 km (4.3 mi) west of Drvar.

[22] On 23 May 1944, a single German Fieseler Fi 156 reconnaissance aircraft flew several parallel runs up and down the Una valley over Drvar at around 600 m (2,000 ft);[23] activity consistent with conducting aerial photography.

This was observed by Street, the acting commander of the British military mission, who assumed it was spotting for a bombing raid and advised both Tito and the Americans.

[25] Despite the intelligence received and observations made by the British, the Partisans appear to have been quite complacent about the threat; Tito's chief of staff, Arso Jovanović, swore that "a German attack was impossible".

The most obvious indicator that Tito was unaware of the imminent attack is that he remained at the Drvar cave overnight on the evening of 24 May, following a celebration, instead of returning to Bastasi.

General der Infanterie[f] Ernst von Leyser, commander of XV Mountain Corps headquartered at Knin, was responsible for the conduct of the operation.

He realised that the gliders and transport aircraft would be insufficient for the whole of the 500th SS Parachute Battalion to be delivered to Drvar in one lift, so he came up with a plan involving two waves.

[35] On 22 May 1944, the 500th SS Parachute Battalion was transported to airfields at Nagy-Betskerek (Zrenjanin), Zagreb and Banja Luka, dressed in Wehrmacht uniforms for security reasons.

[34] The plan for the ground forces of von Leyser's XV Mountain Corps was for nine separate but coordinated thrusts toward the Drvar–Bosanski Petrovac area from all directions.

The party split up and following a creek leading away from the Unac, the small groups climbed the heights to the east and withdrew toward the village of Potoci.

Roughly at the same time, his Partisan counterpart in Drvar, Milan Šijan, the commander of the 3rd Lika Proletarian Brigade, was also wounded by German machine gun fire.

[50] Although its total strength was estimated at 185,500 men in late May 1944,[51] the 2nd Panzer Army was not able to rally more than 16,000 troops for Operation Rösselsprung due to ever-increasing Partisan activity throughout the country.

[53] During Operation Rösselsprung, the Germans rendered these tactics ineffective by combining strong and fast motorised columns with adequate pioneer support.

At 21:00, the 3rd Battalion of the 2nd Lika Proletarian Brigade launched a successful local counterattack on the vanguard of Kampfgruppe Willam, separating it from the main body.

Being fully motorised, it used its mobility to outmanoeuvre the Partisans, bypassing their main defensive positions to the west, the Cossack pioneers playing an important role in keeping the column moving.

As the German intention to encircle the Supreme Command in a small area around Drvar with approaching units, and then destroy it with land forces had become apparent by now, serious reorganisation of Partisan dispositions was required.

The detachment was formed on the night of 25/26 May from the 11th Company of the 13th SS Regiment, several pioneers, and a group of specially trained personnel from the Brandenburg Division.

Out of contact with their corps headquarters, the 4th Krajina Division continued to retain two brigades along the Bihać-Bosanski Petrovac road, even though the 92nd Motorised Regiment had already passed along this route and into their rear.

The critically important Bosanski Petrovac-Ključ road to the south was left unguarded, endangering Tito and Partisan Supreme Headquarters as they fled from Drvar.

[24] Throughout their escape, the British mission were able to maintain contact with their headquarters by radio and continued to call in support from the Balkan Air Force against the German formations taking part in Operation Rösselsprung and the Luftwaffe aircraft in the skies over Yugoslavia.

A costly ground attack was also launched by a combined Partisan, British and United States force on the German-held Dalmatian island of Brač.

[94][95] Late on 6 June, Tito was delivered by the Royal Navy escort destroyer HMS Blackmore to Vis, where he re-established his headquarters and was joined by the Allied missions.

[98] The operation was a failure,[94] as Tito, his principal headquarters staff and the Allied military personnel escaped, despite their presence in Drvar at the time of the airborne assault.

[101] The commander of the 7th SS Division, SS-Brigadeführer und Generalmajor der Waffen-SS[i] Otto Kumm claimed that Partisan losses included 1,916 confirmed and another 1,400 estimated killed, and 161 taken prisoner.