The 'Osovets Offensive Operation' was the Soviet final phase of the 'Belorussian Strategic Offensive Operation', otherwise known as 'Bagration' (6/14 August 1944).

Within 'Bagration', this operation was preceded by the 'Vitebsk-Orsha Offensive Operation' (23/28 June), the 'Mogilev Offensive Operation' (23/28 June 1944), the 'Bobruysk Offensive Operation' (24/29 June), the 'Polotsk Offensive Operation' (29 June/4 July), the 'Minsk Offensive Operation' (29 June/4 July), the 'Vilnyus Offensive Operation' (5/20 July), the 'Siauliai Offensive Operation' (5/31 July 1944), the 'Białystok Offensive Operation' (5 July/27 July), the 'Lublin-Brest Offensive Operation' (18 July/2 August) and the 'Kaunas Offensive Operation' (28 July/28 August).

Osovets is the Russian version of Osowiec, the area of Poland in which the operation took place.

The operation was launched after General Georgi F. Zakharov’s 2^nd Belorussian Front had taken Grodno and Białystok in the 'Białystok Offensive Operation'. The front was issued with new objectives at the end of July, being ordered to move on Łomża (Lomscha in German) and Ostrołęka (Scharfenwiese in German) and to enlarge its bridgeheads over the Narew river in preparation for an advance into East Prussia. The defence was aided to a certain extent by fortifications from previous eras, including a major fortress complex of the imperial Russian period at Osowiec on the Biebrza river. This had been the scene of a siege in 1915 during World War I, and the fortress had been partially demolished by the Germans in 1939 before being transferred to Soviet ownership. There were also substantial Soviet border fortifications remaining from the Molotov Line located some 12.5 miles (20 km) west of the old fortress.

The forthcoming campaign pitted elements of General Friedrich Hossbach’s 4^th Army (General Helmuth Weidling’s VI Corps) and Generaloberst Walter Weiss’s 2^nd Army (General Friedrich Herrlein’s LV Corps), under the overall command of Generalfeldmarschall Walter Model’s Heeresgruppe 'Mitte', against elements of Zakharov’s 2^nd Belorussian Front 1. The offensive began on 6 August with further penetrations to the west of Białystok by the 2^nd Belorussian Front. The approaches to Osowiec were strongly defended, and the 1^st Guards Assault Engineer Brigade had to establish river crossings under heavy fire. Units of the front then stormed and took the fortress, after a heavy air bombardment by Baidukov’s IV Assault Air Corps on 14 August, the day which is noted as the end of the offensive in official Soviet histories, although the Soviet forces continued to seize bridgeheads over the Narew river throughout the rest of the month.

The 49^th Army found it had to overcome the German defences on the approaches to Łomża, however, and took many casualties including General Major Anton I. Iakimovich, the commander of the 343^rd Division, in the course of its attempt to force a passage through the German defensive lines. Łomża itself was not taken until mid-September, and there were intense battles along the Narew river as the 2^nd Army was reinforced and attempted to eliminate the Soviet bridgeheads. Although there were many local actions (including attacks by Polish partisans, who had a strong presence in the area) the German defence line on the Narew river held through the remainder of 1944 to the time of the 2^nd Belorussian Front’s advance in the 'East Prussian Strategic Offensive Operation' of January 1945.

Air support was provided by General Polkovnik Konstantin A. Vershinin’s 4^th Air Army with part of General Major Semyon G. Getman’s 230^th Assault Air Division, part of Polkovnik Valentin Smolovik’s 233^rd Assault Air Division, part of Polkovnik Mikhail Volkov’s 229^th Assault Air Division, part of Polkovnik Vasili Buss’s 309^th Fighter Air Division, and Polkovnik Grigori Pokoyevoy’s 325^th Night Bombing Air Division, General Major Fyedor F. Zherebchenko’s VIII Fighter Air Corps from the 16^th Air Army with Polkovnik Mikhail Yakushin’s 215^th Fighter Air Division, and General Major Georgi F. Baidukov’s IV Assault Air Corps with Polkovnik Nikolai Vinogradov’s 199^th Assault Air Division.