Originally posted by the Voice of America. Voice of America content is produced by the Voice of America, a United States federal government-sponsored entity, and is in the public domain. Iran Standoff Shines Spotlight on New Trump Security Adviser Associated Press WASHINGTON - In a defining week for President Donald Trump on the world stage, national security adviser Robert O'Brien was a constant presence at the president's side as the U.S. edged to the brink of war with Iran and back again. The contrasts with O'Brien's predecessor along the way -- in secret consultations at Trump's Mar-a-Lago resort in Florida, in the Oval Office and in basement deliberations in the White House Situation Room -- could not have been more stark. While former national security adviser John Bolton spent decades as a conservative iconoclast in the public arena, O'Brien is far from a household name. While Bolton had strong opinions he shared loudly in the Oval Office, O'Brien has worked to establish an amiable relationship with Trump. And while Bolton's trademark mustache was a target of Trump's mockery, the president is drawn to O'Brien's low-key California vibe and style. "Right out of central casting," Trump says of O'Brien. .