Did Lord Buddha gain enlightenment by inquiring into death?

I remember one just one of my treasured books 1955 copy of " the teachings of a compassionate Buddha" where I read that the Lord had a morbid fascination with death ..suffering etc and inquiring of death ( possibly a force //entity within)he gained insight into a possible way out of suffering ..rebirth etc pls let me know if this is true ? For example there is reference made to countless past lives of the Buddha by him so I guess he was able to tap into his own death.