The kings of the Island were not unaware of the events in South lndia, the Pandyan empire had been growing at the expense of its neighbours and Sirimara Srivallabha .
We do not know the exact date of the invasion, but it must have taken place in the early part of Sena’s reign. The Pandya king landed with a large army and gradually took possession of the entire Uttaradesa. Sena sent his forces to eject the: enemy from the Island. But, due to discord among the leader of the army, it was of not successful . King Srimara established his position at Mahatalitagama. The tamil who lived In these parts swelled his ranks. When the Yuvaraja Mahinda, who was present at the battle field , saw the fate of his army, he took his own life in the field, rather than that to death at the hands of the enemy. When the news of this debacle was conveyed to the king, he gathered together the royal treasury and fled to Malaya. One of the brothers of king Sena, the Adipada Kassapa, escaped after the battle and fell back on the city’ made a last stand at the northern gate of the capital. But being defeated here, too, he escaped to Kondivita, he confronted the Pandyans at Polonnaruva and was captured and slain.
Sena took up a position well to the south, near where the Mahaveli and the Amban Ganga, meet, and set guards along the high road to the capital to warn him of any impending danger. King Sirimara, however looted, and once satisfied, he was ready to leave. He, therefore, sent his officials to Sena to effect a treaty. Sena was only too glad, for had nothing to lose, and he agreed to all the conditions that were laid down.