After his illumination on the fifth year, the Buddha was dwelling in Kutagarasala in Vaishali. There he saw his father on the death-bed by his divine eyes. He felt the importance of advocating his principles to his father for his spiritual growth, as he was just about to achieve the arahatahood.
Also, besides this, there was a war arisen between the Sakiyans of Kapilavatthu and the Koliyans of Kolanagara over the water-argument of the Rohini river – which differentiated the territories of the two kingdoms. As the Khattiya of the two neighboring kingdoms before much enjoyed the lovely connection; and intermarried and banquet with each other, the Buddha wanted to protect the two countries as well for the sake of them.
The Buddha therefore, went to Kapilavatthu to visit his father, and advocate him to become the one of the arahantas. Soon, Suddhodana became an arahanta and he then died.
After his death, Buddha became the peace moderator for the Sakiyans and the Koliyans. He thus prevent the bloody quarrel between the two neighboring tribes. Both the tribes then encouraged their men to join the Sangha as a token of thankfulness for his mediation; and each extended hospitality by inviting him as its main guest. The Buddha accepted both the invitations and then lived in both the tribes of Kapilavatthu and Koliyanagara in turns.