It fought the advancing Wehrmacht in central Poland, from the area of Skierniewice through the Kampinos Forest to Modlin Fortress, surrendering on September 29, 1939.

Due to rapid Russian advance into Austrian Galicia, the still incomplete regiment, commanded by General Karol Durski-Trzaska was sent in early September 1914 to the town of Khust in Hungary.

The regiment was transported to Bessarabia, where in May 1915 it fought along the Prut river, and on June 4 tried to break through Russian lines, but was repelled.

Three days later, the regiment managed to advance forward, taking positions along the Rokitnianka river (see also Charge of Rokitna).

In late November 1916, the regiment was transferred to Warsaw, and in January 1917 it was moved to Zegrze for training by German rules.

Following the Oath crisis, when some soldiers refused to swear allegiance and obedience to the Emperor Wilhelm II of Germany, the rebels were interned in camps at Beniaminów and Szczypiorno.

After the Treaty of Brest-Litovsk (Ukraine–Central Powers), most soldiers decided to break through Austrian lines and join Polish II Corps in Russia (see Battle of Rarańcza).

Near the town of Kaniv, German and Austrian forces surrounded the Poles, who were commanded by General Józef Haller.

In March 1919, the Third Legions Infantry Regiment was formed in Zegrze near Warsaw, and on April 12, its 1st Battalion was sent to northeastern front, where it was engaged in fighting the Red Army near Lida.

After the Battle of Dęblin and Mińsk Mazowiecki, the enemy retreated in panic, and the regiment was transferred to Krasnystaw, where it fought Soviet 1st Cavalry Army of Semyon Budyonny.

After Żeligowski's Mutiny and the capture of Vilnius by Polish forces, the regiment guarded Polish–Lithuanian border near Druskininkai, until April 1921.

On the next day, German 17th Infantry Division approached Łask, and as a result, Polish forces regrouped and retreated towards Głowno.

On September 8 in the evening, Colonel Edward Dojan-Surowka, who commanded the infantry of the 2nd Legions Division, had a nervous breakdown and abandoned his soldiers.

In the morning of September 12, it was involved in a bloody skirmish near Błonie, after which General Wiktor Thommée decided to withdraw elements of the division to Modlin.

On September 27, 1923, the President of Poland confirmed the new regimental flag, which was funded by the residents of Ostrowiec Świętokrzyski and Opatów.

Among its notable soldiers were such figures, as Władysław Sikorski, Józef Haller, Jan Berek and Henryk Minkiewicz.