'Mihailović' was the German final undertaking to suppress the Serb Četnik detachments of the Yugoslav army, headed by Colonel Dragoljub 'Draza' Mihailović, in the area of Sumadija within German-occupied Serbia (4/9 December 1941).

On 31 August 1941 the Jadar Četnik detachment had freed Loznica from German occupation in the Battle of Loznica, which was the starting point of the Serb uprising against the German occupation. During September the uprising had become larger and the Četniks had liberated the entire Podrinje and Mačva areas with the exception of the town of Sabac. Late in September and early in October the uprising spread to most of Sumadija and the river valley of western Morava (Čačak, Kraljevo and Krusevac).

However, early in October the Germans started their 'Drina' offensive against the Četniks, whereby Generalleutnant Dr Walter Hinghofer’s 342^nd Division from the north and Croat forces attacked from Srem in the south. By the end of October the whole of the Mačva area and the middle of the Podrinje area had been retaken from the Četniks, breaking the siege of Valjevo and, after a break-out to the east of this town, reaching the Ravna mountain area, where the Četniks' main headquarters was located.

During October the Germans carried out mass executions of Serb civilians, up to a total of 10,000, in retaliation for the dead and wounded they had suffered and also to intimidate the population into pacification.

New circumstances late in October between the rival partisan and Četnik anti-Axis groupings led to the outbreak of a fratricidal war, and the Germans temporarily suspended the offensive they had been planning and waited for the communist partisans and royalist Četniks to destroy themselves. However, the Četniks and partisans signed an armistice on 20 November in Čačak, and this prompted the Germans to attack both the partisans and the Četniks between 25 and 30 November. Having successfully undertaken two offensives in the direction of the Drina river and western Morava, the Germans closed the ring around Sumadija.

The Germans decided to focus their main forces on the Ravna mountain area, where the Četnik leader, Mihailović, was headquartered. On 3 December the Germans issued orders stating that the primary objective of 'Mihailović' was the destruction of Mihailović's forces and their headquarters to the south of Valjevo by surrounding and 'cleansing' the Ravna mountain area of 46 sq miles (120 km²). Within this basic objective the Germans schemed to attack the Ravna mountain area from four directions using the 342^nd Division, the formation which had made the greatest contribution to the fight against the Četniks and the crushing of the uprising in the two previous months. The Germans also planned to bolster the physical effect of the offensive with the supposed terror aspect of their order, issued two months earlier, that 100 Serbs were to be shot for every German soldier killed.

Mihailović knew of the concentration of German forces in preparation for the forthcoming offensive, and therefore ordered the dispersion of his men into groups of 12, five and three for ease of undetected movement. Mihailović believed that the German forces would not be able to operate for any length of time in remote area, and therefore that the Četniks would be able to regroup in the area once the German sweeps had passed. For the same reason Mihailović planned not to attempt any direct confrontation with the 342^nd Division which, he hoped, would therefore pass through the operational area without making contact with the Četniks.

On the eve of the offensive, the Četniks successfully implemented a disinformation campaign, supervised by Major Ljuba Jovanović, commanding the gendarmerie station in Valjevo, and this persuaded the Germans that the Četniks were planning to tackle the advancing Germans with their full strength: this effort led the Germans to proceed with greater caution, and therefore less speed, in their progress toward the Ravna Gora (mountain region). Mihailović also planned a special mission for Captain Dragoslav Račić and his forces, which were to operate as a diversion.

Before the start of the Serb uprising, the Germans had been using three divisions headquartered in Belgrade but with their constituent regiments and battalions spread widely through Serbia. These formations were Generalmajor Heinrich Borowski’s 704^th Division, Generalleutnant Friedrich Stahl’s 714^th Division and Generalmajor Paul Hoffmann’s 717^th Division. The beginning of the Serb uprising led to a measure of reinforcement, the 125^th Regiment being transferred from from Thessaloníki on 5 September, and then the 342^nd Division from Germany on 23 September. In mid-November 1941 the Germans transferred another formation, Generalleutnant Friedrich Zickwolff’s 113^rd Division, from the Eastern Front to Serbia. This last formation had suffered heavy losses on the Eastern Front, where its strength had fallen from some 20,000 men to about 14,000.

The main German force to break the Serb uprising was the 342^nd Division, 10,000 of whose 20,000 men were the striking force in 'Mihailović'.

Early in December the command of the royalist resistance forces was located in a number of villages below the Ravna mountain area. Among the Četniks in this headquarters and base area was the Ravna Gora Royal Guard, commanded by Lieutenant Nikola Kalabić and at the time numbering about 500 men. Other units were divided into smaller sections for easier penetration and evasion. These included the Ribnička Brigade under Major Aleksandar Misić and the Takovo Brigade under Lieutenant Zvonimar Vučković, with a combined strength of about 300 men. The largest Četnik unit at the time, with a strength of about 1,200 men, was the Cer Brigade under the command of Captain Dragoslav Račić, and this was located to the south of Valjevo. At Mihailović's headquarters was Captain Duane Hudson, head of the British Special Operations Executive mission.

The 342^nd Division started to move on 4 December 1941, advancing in four columns toward the Ravna Gora. The first column set off from Valjevo and soon reached Divci before breaking out toward Struganik on 6 December, forcing a group of Serb civilians to march ahead of it as human shields.

Before the offensive’s start, Mihailović had ordered his units to withdraw from the Ravna mountain area but then, while at the command post in Bersić, received news at about 12.00 on 5 December that Misić and the Četnik detachment in Struganik intended to confront the Germans frontally. Mihailović ordered Lieutenant Colonel Dragoslav Pavlović and Kalabićss Ravna Gora Royal Guard to break through toward Ovcar Kablar Gorge in accord with the already established Četnik plan. Mihailović, Major Zaharije Ostojić and five other men rode to Struganik and ordered Misić to suspend his action.

The second German column was, on 4 December, in fact the first to set off from Valjevo, but passed the other way around Klinci, advanced through Paune and on 6 December reached Rajković.

The third German column moved off on 4 December from Čačak, went over Gornja Gorijevice during the night of 5/6 December and reached Druzetić, near which was the headquarters of Lieutenant Colonel Dragoslav Pavlović's detachment. Together with an accompanying unit, Kalabić manoeuvred his command under cover of darkness and evaded the German encirclement. On December 6, the third German column moved toward Teočin and then Brajići.

The fourth German column advanced from Kragujevac on 4 December, moved through Gornji Milanovac, and reached Takovo and Gornji Banjani.

Mihailović arrived in Struganik during the evening of 5 December and met Misić.

Early on 6 December, the first German columns passed over the Razboj hill with armour protection and drove into Struganik with a large group of civilians as human shields. The Germans opened fire on the Četniks, who had sought shelter in a nearby forest. To protect Mihailović and save the lives of the hostages, Misić, Major Ivan Fregl and a few Četniks emerged and were taken prisoner, Misić claiming to be Mihailović. The unsuspecting Germans temporarily suspended their attack, which presented Mihailović, Major Zaharije Ostojić and all the other Četniks with the opportunity to escape from the forest in which they had been hiding. The Germans later moved Misić and Fregl to Valjevo where they were tortured and then killed on 17 December.

During the night of 6/7 December Mihailović evaded the German forces to reach Kadina Luka.

The four German columns met on 7 December in the Ravna mountain area to discover that their trawl had netted nothing. The Germans searched the area for several hours before burning nearby villages. Combined into a single column, the Germans then moved to Mionica, where they divided once again to search in different directions.

On the next day Mihailović arrived from Kadina Luke in Teočin near the Ravna mountain, which the Germans had searched on previous day. Because of the increased activity of the German forces at this time, to the south and east of Valjevo Captain Dragoslav Račić adhered to Mihailovićss orders and moved the Cer Brigade from the mountains of Medvednik, to the west of Valjevo near the Drina river, onto Bobija mountain. The Cer Brigade crossed the Drina river in eastern Bosnia on 12 December, and joined the Serb resistance forces commanded by Major Jezdimir Dangić who, in the preceding months, had created a zone liberated from the Ustase and Germans in this part of the so-called Independent State of Croatia.

The Germans ended their offensive on 9 December, claiming to have killed 12 Četnik officers and men, captured 482 men and two women, seized 317 guns, 21,000 rounds of small arms ammunition, three cars, 37 horses, two telegraph stations, one short-wave radio station, etc. What the Germans were pleased to call the 'remnants of [Mihailović's] gang' were now located to the south-west of Valjevo, but these were in fact the Cer Brigade under Captain Dragoslav Račić, which had moved from the Medvednik mountain area to the Bobija mountain area in preparation for a further movement into eastern Bosnia, where the royalist leader was Major Jezdimir Dangić.

The Germans assumed that Mihailović was with these forces, but on 10 December Mihailović was in the Ravna mountain area, in Teočin. The Germans believed that they had broken the royalist resistance in this part of occupied Serbia, but had in fact failed to destroy Mihailović's resistance movement, whose core organisation (a number of headquarters) was based in mountain villages across the country and could readily recruit. Even so, the temporary collapse of the uprising in Serbia allowed the Germans to focus, in the forthcoming months, on the eastern part of the Independent State of Croatia, a territory which at this time was controlled by Serb resistance elements under Major Jezdimir Dangić. The German and Croat forces were already planning an offensive to be launched against this grouping in January 1942.

Up until 21 December Mihailović remained in Teočin, where he was joined by Lieutenant Colonel Dragoslav Pavlović, Major Mirko Lalatović, Lieutenant Nikola Kalabić and Lieutenant Zvonimir Vučković, radio operator Slobodan Likić, and the British Hudson. On 19 December Mihailović had been promoted to brigadier general by King Petar II at the suggestion of the London-based Yugoslav government-in-exile of Prime Minister Dusan Simovic. The continued threat of German pursuit in the Ravna mountain area on 22 December persuaded Mihailović to move to the Vujan mountain area, where he re-established his headquarters in Lunjevica, and then on 12 January 1942 Mihailović found permanent accommodation in a winter house above the village of Jablanica.

At this time, the new president of the Yugoslav government-in-exile, Slobodan Jovanović, appointed Mihailović as the armed forces minister in his cabinet on 11 January 1942. On 19 Petar II further promoted Mihailović, this time to the rank of major general.