Why were Class A war criminals enshrined in Yasukuni?

Was it simply to enshrine those who died in combat for Japan? Just to provide a place for their souls? Or were there calculated political reasons?

Akiko Takenaka of the University of Michigan, who is currently working on a book about the history and politics of the shrine, has written an article for Japan Focus which provides an answer straight from the mouth of the guy who decided to do it.

...new Yasukuni head priest Matsudaira Nagayoshi in July 1978, following the death of head priest Tsukuba Fujimaro, who had strongly opposed the enshrinement of Class-A criminals. Shortly after his appointment, Matsudaira, who had publicly called for reversing the verdicts of the Tokyo War Crimes Tribunal to restore Japan’s national spirit, added the war criminals’ names to the already completed list of names that were to be enshrined during the fall 1978 ceremony. Matsudaira’s eagerness to enshrine the fourteen is demonstrated in his later comment reflecting back on the enshrinement as “the one act of my entire life that I can be proud of.” He went on to explain that he had proceeded with the enshrinement as a way to discredit the Tokyo War Crimes Tribunal. Read the full article here at Japan Focus.

She also covers the connection between the shrine and the LDP, along with it's connection the the LDP's attempt to revise the constitution and revise the history of WW2.