although it utilized experiences learned in 1943. The 3rd Ukrainian Front worked on digging in, creating extensive trench networks ideal for anti-tank defenses, along with defensive earthworks for the artillery and infantry. The main differences between the Soviet defenses during the Battle of Kursk and the Balaton defensive operation (the Russian name for Operation Spring Awakening) was the relative short time frame allowed for defensive preparations (half a month), the smaller number of Soviet forces partaking in the defensive, and a reduced focus on perfecting the defensive lines as after all the 3rd Ukrainian Front would need to start its offensive from these lines. Other minor differences included the lack or limited use of barbed wire installations, anti-tank obstacles, and bunkers, although the 4th Guards Army command did suggest to place the burnt out wrecks of 38 previously destroyed German tanks into advantageous positions; it is unclear how many were actually set up. Tolbukhin's 3rd Ukrainian Front had 5 Armies plus 1 Air Army, in addition it also had the 1st Bulgarian Army with the 3rd Yugoslav Partisan Army also partaking in the defense. The 3rd Ukrainian Front would be set up in a two echelon defensive layout, with the 4th Guards Army, 26th Army, and 57th Army, and the 1st Bulgarian Army in the first echelon, while the 27th Army would be held back in the second echelon for reserve. The 4th Guards Army's three Guards Rifle Corps and one Guards Fortified District would be spread out over a 39 km front and reach 30 km deep, broken into two belts with one behind the other. The 26th Army, which was expected to take the brunt of the German offensive, arranged its three Rifle Corps along a 44 km front but only 10–15 km deep. The 26th Army's Corps' would be layered in two belts whose defensive preparations had originally begun back on 11 February, prior to any sign of German offensive intentions. The 57th Army's one Guards Rifle and one Rifle Corps were spread along a 60 km front and 10–15 km deep; the Army would receive another Rifle Corps during the fighting. The 27th Army's one Guards Rifle and two Rifle Corps would remain in reserve unless the situation in the 26th Army called for its use. Held in reserve, the 3rd Ukrainian Front also had the 18th Tank Corps and 23rd Tanks Corps, along with the