His first major success was a series of live-action short films called "Alice in Cartoonland" (1923-1927). These films combined live-action footage of a young girl named Virginia Davis with animated characters.
It wasn't until 1927 that Disney began producing his first fully animated film, "Steamboat Willie", featuring Mickey Mouse. This film was groundbreaking for its use of synchronized sound and was a huge success, paving the way for Disney's later animated feature films.
So, while Disney initially started with live-action, he saw the potential of animation and quickly shifted his focus towards it, becoming a pioneer of the medium.