To better understand this story it is recommended to first read Dragon ball Multiverse's chapters 20,21,64,65.
Age 737, planet Kanassa.
This planet was the latest conquest of Frieza's empire and it's inhabitants were the latest casualties. The invasion was lead by Frieza's best soldiers: the Saiyans, and this particular group was lead by a saiyan born into the lower class but that was now was able to rival the elite of his species: Bardock.
The saiyan race thanks to their innate ability to turn into great and powerful apes called ozaroos, and thanks to their incredible lust for conflict were able to decimate 80% of the population in a matter of days, but on this planet an event would occur that would have massive ramifications for the entire universe. After a long night of killing and destroying everything in their path the saiyan invaders were now resting to recover their strenght.
While he was laying on the ground Bardock's scouter read a lonely but high power level, intrigued by this the saiyan decided to attack the source of this power all by himself leaving his team behind. When he reached the source that his scouter detected he saw one of the remaining members of the species that they were slaughtering. The alien told Bardock to listen to what he had to say before killing him. The saiyan wasn't having non of it and raised his arm to charge an attack, but he then decide to stop, the saiyan had chosen to listen out of pure curiosity.
The alien then when on to tell him that he already knew his planet would have been invaded but when he tried to warn his people but they all didn't belive him. He then told bardock that he knew his race was enslaved by a horned tyrant and that he was the one that ordered his race extinction, Bardock was shocked, his race didn't have the technology to know about Frieza.
"I also saw the future of your people and it's as bleak as ours, the horned demon will destoy your planet and kill you all" the strange alien said while looking at the scarred saiyan.
"why are you telling me all of this?" Bardock asked confused.
"Because I want revenge against that tyrant, he sent you to kill us" the Kanassian answered.
"To receive my powers you must not kill me from afar, pierce my heart with your hand instead" the alien explained to the saiyan.
The father of Goku did as he was told and the blessing or curse of knowing the future was now his.
After killing the alien Bardock felt a crushing pain as if his head was about to explode, then all of a sudden images of the future appeared in front of him: his squad murdered, King Vegeta dying, his last stand against the tyrant, and a blinding light caused by the explosion of his planet. Bardock was shocked, the alien didn't lie he now had the ability to look into the future, no now he also had the ability to change it.
"I have to act quickly" the saiyan thought. He then returned to his team, but Bardock already knew that Frieza will send Dodoria to kill them so he ordered them to immediately abandon this planet and return to Planet Vegeta
Age 737, planet Vegeta.
Bardock and his squad landend on their home planet, their squad leader then immediately rushed to the throne room, his squad following him without knowing what he would do next.
"King Vegeta terrible things are going to happen, Frieza will come to our plaent and eradicate us! We need to prepare" the scarred saiyan yelled immediately catching the attention of all the people present in the room, the Saiyans started laughing and mocking him in response. Even Bardock's squad didn't belive their leader, thinking he had gone insane from the paranoia.
"Dammit! It's the same thing that happened to that alien, I won't be able to change the future if the don't listen to me" Bardock thought as he had another premonition, he saw once again Frieza killing the king in a single blow to the chest and the then he saw his own death by the hands of the tyrant. Bardock grit his teeth, he now understood that if he wanted to save his race he had to take some drastic measures.
"All I need is to be listened to" Bardock thought then he turned to face the king and pointed a finger at him.
"King Vegeta according to saiyan tradition I challenge you for the throne, the saiyans follow their king and that position can go only to the strongest of us" the father of Raditz yelled shocking once again everyone present in the room.
"Insolent! You'll have to fight me first" a long haired saiyan elite yelled.
"No way Gerkin I challenge the king not you" Bardock simply answered.
"Very well Bardock, I accept your challenge!" the king explained as he rushed the once low class warrior, the two powerful saiyan began to clash, after a few minutes of fighting it was obvious that Bardock was on different level when compared to king, he had gained experince and strenght on the many campaigns he fought while the king was ruling his planet. With the fight won Bardock pulled King Vegeta's tail and went to sit on his new throne.
"I challenge you for the throne" Gerking immediately said as he prepared to fight the new king.
"I accept, but according to saiyan tradition I can have one week of rest from my last fight" Bardock explained, now as their new king the saiyan had to listen to him and Bardock started to make preparations for the tyrant's arrival.
The next day Bardock was finishing up his plan to take down Frieza when all of a sudden he received a call from his mate Hanasia.
"Have you gone completely insane?" the female saiyan yelled in her scouter, her screams made Bardock deaf for a few moments.
"If this story about Frieza turns out to be false I will personally defy you for the throne and kill you" the saiyan elite soon added.
"Sure, you can come after Gerkin" Bardock answered with a grin.
"Oh by the way I have trained our son Kakarot, now that he has become a little stronger he won't have any trouble exterminating the population of that planet" Hanasia said as she changed the subject of their conversation.
Bardock by that point had completely forgot about his second son Kakarot as he was occupaid in more important matters than being a parent.
"I never liked Frieza's stupid methods, sending one of our babies to exterminate a planet instead of just invading it, but if I don't send him to Earth Frieza might get suspiscious and I don't want to ruin my own plan, and after all I don't care about that weakling of my son" Bardock thought for a few seconds.
"Mighty king Bardock" Hanasia said mockingly.
"are you still there? What should I do?" she added.
"Er, yes send Kakarot to Earth, once Frieza is dealt with we'll send someone to pick him up once he has finished his mission" Bardock answered as he snapped from his trance.
Bardock didn't know it yet but he had just made a decision that would have massive consequences for the future of the universe and of the saiyan race.