The Cumans, who had emerged as the dominant power of the Pontic steppes in the early 1060s, invaded the southern regions of Kievan Rus' in 1068. The three brothers together marched against the invaders, but the Cumans routed them on the Alta River. From the battlefield, Sviatoslav withdrew to Chernigov and regrouped his troops. He returned to defeat the Cumans with a smaller force at the town of Snovsk on 1 November, thus enhancing his prestige among the populace. In the meantime, the townspeople of Kiev had dethroned and expelled Sviatoslav's brother, Iziaslav. Taking advantage of Iziaslav's absence, Sviatopluk sent his own son, Gleb to Novgorod to rule the town. Iziaslav returned at the head of Polish reinforcements. The townspeople of Kiev sent messages to Sviatoslav and Vsevolod, imploring them to come to their "father's city" and defend it, according to the "Russian Primary Chronicle". Sviatoslav and Vsevolod requested Iziaslav "not to lead the Poles in attack upon Kiev", stating that "if he intended to nurse his wrath and destroy the city, they would be properly concerned for the ancestral capital". Iziaslav partially acquiesced: he did not let his Polish allies enter the town, but his retinue slaughtered or mutilated many of his opponents in Kiev. He also attempted to punish Anthonythe founder of the Monastery of the Caves in Kievwho had supported his enemies, but Sviatoslav gave shelter to the saintly monk in Chernigov. With Iziaslav's return to Kiev, the "triumvirate" was restored. The three brothers together visited Vyshhorod in order to participate in the translation of the relics of their saintly uncles, Boris and Gleb on 3 May 1072. According to "The Narrative, Passion, and Encomium of Boris and Gleb", Sviatoslav took Saint Gleb's hand and "pressed it to his injury, for he had pain in his neck, and to his eyes, and to his forehead" before placing it back into the coffin. In short Sviatoslav felt a pain at the top of his head and his servant found a fingernail of the saint under his cap. Most historians agree that the three brothers expanded their father's legal code on this occasion, but the exact date is unknown.