Take down a government building. McVeigh truly believed that he had two comrades in arms...

Himself - Writer: Tim McVeigh had read in "The Turner Diaries" of how, generally, you could build a truck bomb. He found other articles that told him exactly how to build a truck bomb. He wanted to do what Earl Turner did: take down a government building.
Himself - Biographer: McVeigh truly believed that he had two comrades in arms in Terry Nichols and Michael Fortier. They go back to the Army. They all like "The Turner Diaries". They all shared the same anti-government thoughts. They all wanted to show that somebody could attack the U.S. government, that it was that vulnerable. To get started, they knew that they needed the main ingredient, which was fertilizer.
Himself - Journalist: They start to buy bag after bag after bag of ammonium nitrate. Tim McVeigh and Terry Nichols break into a storage shed at a quarry and they steal these explosive Tovex sausages, which will make the bomb more powerful.
Himself - Writer: It wasn't easy to get some of this stuff. Some of the explosives were not available to the average citizen. They spent months and months getting the parts of this bomb together. Fortier's role was very, very limited. Nichols had a bigger role, but really just following orders from McVeigh.
Himself - Journalist: And then, Tim McVeigh manages to get some 55-gallon drums of nitromethane racing fuel. The bomb that was depicted in "The Turner Diaries" was ammonium nitrate and fuel oil. McVeigh was going to amp up his bomb really dramatically by using this much, much more volatile fuel