According to investigators, the 34-year-old U.S. Soldier had been inspired by ISIS over at least a five-year period.

Army Sergeant First Class Ikaika Kang appeared in federal court in Honolulu on Monday accused of attempting to provide "material support or resources" to ISIS.

Court papers describe how Kang handed over 18 "Secret-level" military documents to undercover agents he believed could help ISIS.

On Saturday, before his arrest, he pledged allegiance to the Islamic State, and made combat training videos, he believed would be shown to ISIS fighters.

Kang enlisted in the Army just months after the 9-11 attacks and served one tour in Iraq.

In 2012, Kang had his military clearance revoked for making pro-Islamic state comments.

Kang was eventually reinstated, and in 2013 was deployed to Afghanistan.

The Department of Justice has announced a series of terrorism-related arrests in recent weeks.

The FBI has said it is investigating hundreds of terrorism cases across the country.