When the Partisan 2nd Proletarian and 5th Krajina divisions advanced into Serbia in March 1944, Partisan forces in northern Montenegro and the Sandžak were reduced to the 37th Sandžak Division. To exploit this weakness, Đurišić proposed to the Germans that they launch an offensive operation. Operation Frühlingserwachen was planned for the northern parts of Montenegro and the Sandžak; its primary objective was the capture of Kolašin through concentric attacks launched from Pljevlja, Prijepolje and Pešter. This would permit them to link up with forces advancing from Podgorica in the south and to drive a wedge through the middle of the Partisan lines. Operation Frühlingserwachen involved an Axis force of about 5,000 men comprising some of Đurišić's forces, the SS Polizei-Selbstschutz-Regiment Sandschak, the 2nd Battalion of the 5th Regiment of the SDK, and two reinforced German motorised companies. The operation began on 9 April; on 12 April they reached Bijelo Polje. Đurišić's forces seized Berane on 17 April, but the 37th Sandžak Division halted the advancing forces on the line of the Tara River at Mojkovac. On 24 April, after nine days of attacks and counter-attacks, the 37th Sandžak Division, reinforced by the 7th Montenegro Youth Brigade "Budo Tomović" of the 3rd Shock Division, regained the initiative. They retook Bijelo Polje on 30 April, and Berane on 5 May.