Instead of fighting with the earths forces the Saiyans planted 6 Saibermen each one would fight with an Earthlings. First to fight was Tien he easily overcame the Saiberman and as Vegeta was angry due to defeat he killed the saiberman. Yamcha was next to fight.

Yamcha overcame the saiberman until he self-destructed killing both of them. Krillin then used a ki attack to destroy the remainder of the saibermen except one which Piccolo destroyed.
Nappa then entered the battle and was much stronger than any of the z-warriors. Choatzu self-destructed in hope to bring him down but he was unaffected. Tien then went all out but was also destroyed by the Saiyan giant Nappa. A pause for 3 hours so that Vegeta could wait for Goku to arrive so they could fight tool place, Nappa was bored so destroyed the earths army. Goku didnt show up so the fighting resumed, Nappa went for Gohan but Piccolo stepped in the way. It was just Gohan and Krillin who were losing easily until Goku showed up with a PL greater than Nappas. Goku took care of Nappa unveiling a new attack , The Kaio Ken.

upset by Nappa Vegeta then killed him saying how worthless he was. Vegeta and Goku decide to take the battle eslewhere and to fight alone.
After moving to another part of the planet the battle begun with the two seeming evenly matched, Vegeta then managed to get the advantage but Goku powering up with his Kaio Ken managed to stay in the running. A power struggle then took place, Gokus KameHameHa versus Vegetas Galick Gun, Goku won but hadnt one the fight. Vegeta then returned to earth angry, he annouced how Saiyans can transform and told Goku about how Gokus father invented artificial moonlight so they could easily transform. Vegeta then threw his artifical moon into the air and begun to transform. Vegeta was easily beating Goku in his Oozaru.