On 15 February, protesting against the Treaty of Brest-Litovsk which reduced the chances for the creation of an independent Poland, the II Brigade of the Polish Legions, formerly part of the Austro-Hungarian Army, broke through the frontline near Rarańcza and merged with the Polish units formerly in the Russian Army, joining the newly formed Polish II Corps in Russia. The Germans, however, saw the II Corps as troublesome, and decided to ensure it would be disarmed, or would otherwise be incapacitated.

On 18 April the II Corps was ordered by the Regency Council to stop near Kaniv in Ukraine; in a triangle between Potok, Kozin and Stepańce. Soon it begun to be surrounded by a nearby German units. On 6 May the commander of the 28th German Landwehr Brigade, General Zierhold, subordinate of Marshal Hermann von Eichhorn, issued an ultimatum to the II Corps, demanding it lay down its arms and surrender. II Corps readied for battle, and surprised Zierhold, who was unprepared for battle. Zierhold backed down saying that the ultimatum was a miscommunication. Soon however Zierhold received reinforcements, which convinced him he has enough strength to force the issue.

Battle

On the night of the tenth of May to the eleventh of May 1918, II Corps was surrounded and attacked by German units. Polish units, initially surprised, formed on the village of Jemczycha and took defensive positions. The II Corps resisted for about a day, and both sides sustained heavy losses. By the evening of 11 May the Germans, who did not expect the Poles to put such a stiff resistance, proposed a ceasefire and negotiations. With supplies running low the Poles accepted the offer to negotiate, and eventually agreed to an honorable capitulation.

Aftermath

The battle resulted in heavy losses for the Germans, estimated at about 1,500 dead and 273 wounded. Polish losses are estimated to be much smaller, at about few dozen killed and about 150 wounded. Half of the Polish survivors were arrested and sent to prisoner of war camps (number of prisoners is estimated at about 3,250; another estimate suggests 4,000 imprisoned, and 1,500-2,000 who escaped), but the others managed to escape. Those who escaped included the Polish commander Józef Haller de Hallenburg, who faked his death in the battle, and fled to France where he was later appointed commander of the new Polish unit, the Blue Army (or Haller's Army). In the Second Polish Republic, several units would adopt the name "of Kaniów" in honor of that battle: the 28th, 29th, 30th and 31st Infantry Regiments (of Kaniów Rifleman, Polish: Pułki Strzelców Kaniowskich") and 6th Uhlan Kaniów Regiment (6 Pułk Ułanów Kaniowskich).