The battleships from Il'vhin Ghardé were an immediately game changer. Not expecting an attack from outside the blockade, and too spread out to warn each-other of oncoming attacks, Balder's fleet were sitting ducks. The battleship cannons tore into the Hjarta blockade one by one, decimating the entire fleet and sinking it to the bottom of the sea. Now, the tides of the war conclusively turned, Einar's fleet set sail for Hjarta. Unlike Balder, Einar didn't have the patience for a prolonged blockade, and decided to take the fight straight to the heart of Hjarta.
With nearly Balder's entire army on his now-sunk galleys, he was completely defenceless. Einar's army marched through Balder's capital completely unchallenged. He arrived in the Hjarta council building to find it completely deserted, and Balder gone. That might be a problem, but one for him to solve in the future. For now, Einar was in complete control of two of Holm's islands, and with his newfound naval might, there was no doubt that the other two would soon fall to him.
That's what Balder thought too, which is why he immediately fled to Kari's territory upon discovering that his fleet had been sunk. Knowing that he could not win the war without his capital, he pledged himself and his remaining guard to serve Kari, because admitting defeat and pledging to serve a former enemy was infinitely better in his mind than letter Einar win. With that, Kari and Balder began preparing their desperate defence against Einar's oncoming navy.