Why was Armenian once thought to belong to the Iranian language group?

The Armenian language was once erroneously considered a dialect of the Iranian languages due to its historical and cultural proximity to the region.1

For many centuries, Armenian culture was fundamentally Iranian, and the language absorbed a significant number of loanwords from ancient Iranian, which were fully integrated into its vocabulary. Because of this deep-seated influence, early scholars mistakenly classified Armenian as a branch of the Iranian language group.231

In reality, Armenian forms a separate, independent branch of the Indo-European language family. While it shares features with the satem group of languages—which includes Indo-Iranian and Slavic—it also preserves characteristics of the centum group, such as certain k-like sounds. Modern linguistic analysis confirms that its distinct evolutionary path distinguishes it from the Iranian group, despite the extensive historical borrowing that previously obscured its classification.13