'Teslić I' was a German and Croat operation against the partisan forces of Josip Broz Tito in the puppet state of Croatia in Axis-occupied Yugoslavia (5/7 January 1943).
The undertaking’s objective was to retake the town of Teslić in western Bosnia, which had been captured on 2 January by units of the 1st Proletarian Assault Division. The Axis forces involved were, for the Germans, the 1/378th Grenadierregiment, 3/738th Grenadierregiment, Volkdeutschbataillon/738th Grenadierregiment, 1/750th Grenadierregiment and 2/750th Grenadierregiment of Generalleutnant Johann Fortner’s 718th Division and the 105th Panzerzug armoured train, and, for the Croats, the 4/1st Regiment, 1/8th Regiment, 4/8th Regiment, 1/15th Regiment, 115 men of the 'Teslić' Volunteer Militia, Četnik auxiliaries, and Croat air force air support units.
Attacking from the direction of Doboj, Tesanj and Maglaj, the Axis forces drove the partisans out of Teslić and secured the town. The Germans claimed the operation’s casualties as 35 Germans dead and 89 wounded, one Croat killed and 32 wounded, and 134 partisans dead and 117 captured.