During the German summer offensive of 1915 Warsaw was taken by the Central Powers and Bułak-Bałachowicz's unit was forced to retreat towards Latvia. On September 5 he volunteered to lead a group of 72 officers who were ordered to create a partisan unit behind the enemy lines. The group joined a bigger partisan unit of colonel Punin, where Bułak-Bałachowicz quickly rose to the grade of a squadron commander. His unit was formed of four cavalry platoons: one of Cossack light cavalry, one of hussars, one of uhlans and one of dragoons. Thanks to the versatile and flexible structure of his unit, Bułak-Bałachowicz managed to continue the fight behind the enemy lines until 1918.
Soon after its creation, Bułak-Bałachowicz was ordered to quell the so-called Baron Korff Revolt in the area of the city of Luga. With his regiment (the unit was still not completely formed) he reached the area and pacified the peasant unrest without the use of force. He was immediately called in to Saint Petersburg by his superiors, but was afraid of being arrested. Because of that, Bułak-Bałachowicz with his cavalry regiment deserted and moved across the Bolshevik lines to the area of Pskov, held by the joint forces of White Russian Northern Army and various German anti-Bolshevik units. Initially the unit fought against the Reds on the White side, but soon conflicts with the German officials arose and Bułak-Bałachowicz had to switch sides yet again. Together with his battle-hardened unit he disarmed the German units surrounding him and broke to the rear of the Red-held territory. From there he fought his way across the fronts to Estonia, where he finally joined the forces of General Nikolai Nikolaevich Yudenich's North-Western Army. A skilled commander, Bułak-Bałachowicz added greatly to the Estonian victories in the battles of Werro, Neuhausen and Dorpat and was soon promoted to lieutenant colonel.
On May 10, 1919, Bałachowicz was given the command over an assault group and was ordered to drive it to the rear of the Bolshevik lines. Three days later his forces took the town of Gdov by surprise and on May 29 Bałachowicz entered Pskov. For this action he was promoted to colonel by General Yudenich himself. Because of his victories, his subordinates (mostly Belarusian, Cossack, and Polish volunteers) nick-named him ataman, though some preferred to use the term Bat'ko - father.
Bułak-Bałachowicz became the military administrator of Pskov. He personally ceded most of his responsibilities to a democratically elected municipal duma and focused on both cultural and economical recovery of the war-impoverished city. He also put an end to censorship of press and allowed for creation of several socialist associations and newspapers, which enraged White generals towards him. Finally, Bułak-Bałachowicz entered in contact with Estonian officers and Poles who were trying to reach the renascent Polish Army, which was seen by Bałachowicz's superiors as a sign of lack of loyalty. After Pskov was yet again lost to the Bolsheviks in mid-July, general Yudenich ordered Stanisław Bułak-Bałachowicz to be arrested even though only a few days earlier he promoted him to major general (a move Yudenic undertook with hopes of appeasing Bułak-Bałachowicz and encouraging greater subordinance).
However, once again Bułak-Bałachowicz evaded being captured. He handed over his division to his brother Józef and, together with 20 of his friends, left for Estonian-controlled Ostrov. There he once again created a partisan unit. With 600 men he broke through the Red Army front and started to disrupt its supply lines. Despite Yudenich's hostility towards Bułak-Bałachowicz, the latter cooperated with White Russian units during their counter-offensive in the autumn of 1919. His unit captured the railway node in Porkhov and broke the Pskov-Polotsk rail road, which added greatly to the White Russian's initial success. On November 5, 1919 his unit yet again entered the area between Pskov and Ostrov and destroyed the three remaining railway lines linking Pskov with the rest of Russia. However, Yudenich's army could not link up with the areas controlled by Bułak-Bałachowicz and their assault was finally broken.
On January 22, 1920, general Yudenich signed an order of dissolution of his badly-beaten army. On January 28 general Bułak-Bałachowicz, together with several Russian officers and the Estonian police arrested him. A large amount of money was found with him (roughly 227.000 pounds, 250.000 Estonian marks and 110.000.000 Finnish marks) was given to the soldiers of the disbanded army as a last salary, which greatly added to Bałachowicz's popularity amongst them.
Transferred to Brześć Litewski, the Bułak-Bałachowicz's unit was reformed into a Bułak-Bałachowicz Operational Group, sometimes incorrectly referred to as Belarusian-Lithuanian Division. It was composed mostly of Belarusian volunteers, as well as veterans of the Green Army and former Red Army soldiers, and received the status of an allied army. Because of the composition of his troops, Stanisław Bułak-Bałachowicz is sometimes referred to as a Belarusian.
Formally independent, the division was one of the most successful units fighting in the ranks of the Polish Army during the Polish-Bolshevik War. The unit entered combat in late June 1920 in the area of Polesie Marshes. On June 30 Bułak-Bałachowicz once again broke through the enemy lines and captured the village of Sławeczno in today's Belarus, where the tabors of the Soviet 2nd Rifle Brigade were stationed. The enemy unit was caught by surprise and suffered heavy losses. On July 3 the enemy unit was completely surrounded in the village of Wieledniki and was annihilated. After that action, the Operational Group was withdrawn to the main lines of the Polish 3rd Army and after July 10 it defended the line of the Styr river against Red Army actions.
On July 23, during the Bolshevik offensive towards central Poland, general Bałachowicz's group started an organised retreat as a rear guard of the Polish 3rd Army. During that operation, Bułak-Bałachowicz abandoned the withdrawing Polish troops and stayed with his forces for several days behind the enemy lines only to break through to the Polish forces shortly afterwards. During the Battle of Warsaw overnight of August 14 Bałachowicz's forces were ordered to start a counter-attack towards the town of Włodawa, one of the centres of concentration of the advancing Russian forces. On September 17 the area was secured and the Bułak-Bałachowicz's forces defended it successfully until September 7 against numerically superior enemy forces. Stanisław Bułak-Bałachowicz organised an active defence and managed to disrupt the concentration of all enemy attacks before they could be started. For instance on August 30 and September 2 his forces, supported by the Polish 7th Infantry Division, managed to attack the Soviet 58th Rifle Division from the rear, before it could attack the town of Włodawa.
On September 15 the unit was yet again advancing in pursuit of the withdrawing Red Army. That day the unit captured Kamień Koszyrski, where it took more than 1000 prisoners of war and the war materiel depot of an entire division. During the Battle of the Niemen River Bałachowicz's unit prevented the enemy from forming a defensive line in Polesie. Overnight of September 21 his unit outflanked and then destroyed completely the Bolshevist 88th Rifle Regiment near the town of Lubieszów. Perhaps the most notable victory of the Bułak-Bałachowicz's Group took place on September 26, when its forces once again broke through enemy lines and captured Pinsk. The city was the most important rail road junction in the area and was planned as the last stand of the Bolshevik forces still fighting to the west of that city. After it was lost, the Red Army central front collapsed and the withdrawal turned into a panic retreat.
On November 2, 1920, his units were renamed the Russian People's Volunteer Army and transferred to the areas that were to be abandoned by the Polish Army and become a no-man's-land until the final Russo-Polish peace treaty was signed. Three days later his forces crossed into Russian-held Belarus and started an offensive towards Homel. General Bułak-Bałachowicz was hoping for a Belarusian all-national uprising against Bolshevik Russia. His forces initially achieved a limited success and captured Homel and Rechytsa. On November 10, 1920 Bułak-Bałachowicz entered Mozyr. There, two days later, he proclaimed the independence of Belarus and started forming a new Belarusian National Army. On November 16 he also created the Belarusian provisional government. However, the planned uprising gained little support in the Belarusian nation tired by six years of constant war and the Red Army finally gained an upper hand. On November 18 Bałachowicz abandoned Mozyr and started a withdrawal towards the Polish frontier. The Belarusian troops, hardened by the years spent behind the enemy lines, fought their way to Poland and managed to inflict heavy casualties on the advancing Russians while suffering negligible losses, but were too weak to turn the tide of war.
On November 28 the last organised unit under his command crossed the Polish border and was subsequently interned. The Russian government demanded that General Bułak-Bałachowicz be handed over to them and tried for high treason. The Riga Peace Conference was even halted by these demands for several days, but eventually these claims were refuted by the Polish government which argued that Bułak-Bałachowicz was a Polish citizen since 1918.
After the capitulation of Warsaw, general Bułak-Bałachowicz (formally retired) evaded being captured by the Germans and returned to civilian life. At the same time he was the main organiser of Konfederacja Wojskowa (Military Confederation), one of the first underground resistance groups in German and Soviet-occupied Poland. In early 1940 the Gestapo found out his whereabouts. He was surrounded with a group of young conspirators in a house in Warsaw's borough of Saska Kępa and arrested by the Germans. He managed to kill one of them with a knife hidden in his walking stick and was subsequently shot to death by the remaining Gestapo agents. Neither the exact date of his death nor the place of his burial are known.
For his resistance against Bolshevik forces that killed local Belarusian peasantry, members of Belarusian minority in Poland regard him as their national hero. White historians have often seen him to be an adventurer.