The Horsemen were originally created by Chang Tzu's Science Squad for Intergang to kill the Black Marvel Family. They first created Famine (AKA: Sobek) to infiltrate the team and then sent the other three to cause havoc and misery in Kahndaq. It wasn't until the death of Osiris that they revealed themselves to both Isis and Black Adam.
To avenge his fallen brother-in-law, Black Adam fought both Famine and War and killed them both while Isis was had to fight Pestilence. She became infected with a deadly disease, leaving her open prey for Death.
With his wife gone, Adam killed Pestilence and chased Death, which soon lead to the destruction of Biayla, where Adam killed thousands of people. The casualties there gave Death a mass power boost, but that wasn't enough to stop the Black Marvel from having his vengeance.
Shortly after 52, The Horsemen return to spread their evil on the world and having to fight Batman, Superman, and Wonder Woman.