The United States seems to be moving closer to a conflict with Iran — and the man at the center of it all, national security advisor John Bolton, has been pushing for US engagement with Iran for decades. Over the years, Bolton has held some controversial stances, including advocating for preemptive military strikes on North Korea and Iran, and regime change in the latter. As a undersecretary in the State Department during the George W. Bush administration, Bolton also pushed the now-discredited belief that Iraq was in possession of weapons of mass destruction.  Here's how Bolton went from being a mid-level bureaucrat in the Reagan administration to the most important person directing US national security policy.  Visit Business Insider's homepage for more stories.

The United States seems to be moving closer to a conflict with Iran— and the man at the center of it all, national security advisor John Bolton, has been pushing for greater American engagement in the region for decades.

Bolton, a graduate of Yale law school, began working on foreign policy and national security issues under the Reagan administration in the early 1980s, where he quickly developed a reputation as a defense hawk skeptical of the US bureaucracy and international institutions.

Over the years, Bolton has held some controversial stances, including advocating for preemptive military strikes on North Korea and Iran, regime change in the latter, and pushing Russia for harboring Edward Snowden.

As an undersecretary for arms control in the Bush administration, Bolton also pushed the now-discredited belief that Iraq was in possession of weapons of mass destruction which served as the justification for the US invasion of that country.

He later served as the US ambassador to the United Nations — an institution he routinely criticized as ineffectual — where he continued to push for sanctions on countries accused of possessing or developing nuclear weapons.

Bolton has now been Trump's national security advisor for a little over a year, and he may be close to realizing his decades-long vision of the US engaging in a direct confrontation with Iran, according to a recent profile of Bolton published in the New Yorker.

Here's how Bolton went from being a mid-level bureaucrat in the Reagan administration to the most important person directing US national security policy.