Arthas himself was actually really incompetent Lich King

[Europe-dun-morogh]

World of Warcraft happens 4 years after Burning Legion was defeated. Arthas became the Lich King somewhere between End of Frozen Throne - World of Warcraft. In this time he consumed Nerzhul’s spirit and became the dominant personality as the Lich King.

When Nerzhul was the Lich King. He created the Scourge in Northrend, defeated Nerubians, lured Kel’thuzad to Northrend who began the plague in Lordaeron which in result destroyed the northend kingdoms & also summoned Burning Legion to Azeroth for the second time. He also orchestrated the downfall of The Burning Legion & made a plan to protect himself from Kil’jaeden’s agent.

Under Arthas’ reign Scourge lost control in the Plaguelands, provoked Horde & Alliance to launch an invasion to Northend. This invasion resulted in Arthas’ death & dismantlement of the Scourge as a Azerothian super power. So in around 6 years Arthas managed to destroy of the one most powerful kingdoms Azeroth had ever seen, but didn’t achieve anything at any point.

So in short Azeroth wasn’t exactly saved by the heroes of Horde & Alliance alone. Rather the bigger factor was that Arthas was very incompetent Lich King.

Any thoughts am I missing something on his story?

[Geist-silvermoon]

He sure tried to expand

; As this ‘‘third party’’ there were no other choice then to tackle both Horde and Alliance.

A smart ‘‘dictator’’ would not have fought both factions at the time

[Belodine-mirage-raceway]

He wasn’t really interested in getting territories, but rather the mightiest mortals to be his generals. You could argue it was hubris on his part, but without the literal deus ex machina Tirion empowerment out of left field it would have worked and nothing could really stop him then.

[Qulzan-die-aldor (Qulzan)]

Yeah the story wasn’t great.

He destroyed two kingdoms though. Zul’Drak and Azjol-Nerub. He also brought some Vrykul to worship him.