The events I am talking about take place after Warcraft III single-player campaign.

The New History - Chapter I: Armius the Brave.

Right after Archimonde died at the World Tree, Undead under Dreadlord Mal Tholas tried to escape back to their homes, but Thrall and Jaina with Human and Orc reinforcements arrived in time and slaughtered them.

The Undead that were in Northrend survived, because that as soon as the news reached Nerzhul, the Lich King, he ordered Kel Thuzard and his Frost Wyrms to establish a wall of ice blocking Northrend from outer world. But 1 ship broke through. It was with Arthas and the survivors, who returned to serve Lich King in his frozen world.

Night Elves still were living for long time, but they were now as mortal as everyone else. They built their cities in Ashenvale, and soon, Night Elf Kingdoms begun to prosper. Magic was again allowed, and some of High Elves returned to see, how their relatives evolved through 10,000 years.

Orcish Horde settled down in Barrens of Kalimdor, in alliance with Wyverns and Tauren, and finally, dream of many Orc generations came to be true - Orcs were no longer just a horde, but also a political state, the Orcish Empire, with Thrall as emperor, and Cairn as the governor of all the Tauren Province.

Only Humans didn't find themselves a place to stay, until they decided to come back to rebuild Lordaeron. They were followed by Dwarves and some evacuated High Elf warriors. But soon, some of then decided to explore what lays to the east of High Elven lands. They were led by a young and ambitious paladin - Armius the Brave.

Armius came from a poor family, and was recruited during the second war. He became a paladin closer to the end of the third war, during which Portal was destroyed, and remainders of the horde were either captured either were hiding in the mountains. However after that, Armius was busy fighting Troll pirates, while a young Orc gladiator named Thrall run away, and begun a revolution, defeating army after army, and rescuing Orcs. Meanwhile, there was a civil war in Lordaeron, after which, it was too late for the humanity. A new Horde rised up, but it didn't attack humans, until they captured Grom Hellscream. But the rest is history.

Armius then fought under Arthas, however later, he left with Jaina and some other people that believed in Medivh's warning. In Kalimdor, he hardly escaped death from Orcs, Night Elfs and finally the Undead during a massive air attack. Afterwards, he fought Demons, but Human fort blocking the way to the summit eventually fell, and he escaped with Jaina to the other Human settlement.

In Lordaeron, he saw no opportunity after returning, so he decided to set sail to the east on a ship he captured during a war with Troll pirates, which he was hiding afterwards in a small cave in High Elven lands.

They set sail at dawn, after buying enough provision to last for half a year. He and 60 other humans were sailing towards a new destiny. And a new land.