In Gemini City, with Arthas's command, the undead army and the cannon fodder from other races outside the city walls immediately launched an attack on the orcs.
The orc portal was enormous, much larger than the one used in the previous attack on Gemini City. Thousands of orcs poured out every second.
This portal was constructed by the orc priests through the sacrifice of lives, creating a void gate. The orcs seemed to appear out of thin air through a thin membrane. This meant the teleportation array on this side couldn't be destroyed to stop the orcs' advance.
The orcs had learned their lesson.
The first wave consisted of Standard level and Commanding level orcs—essentially cannon fodder. The undead were now locked in battle with them.
The 100,000-strong ground undead army initially overwhelmed the orcs in numbers, creating chaos outside the city walls.