By The Washington Post · Carol D. Leonnig, John Hudson, Reis Thebault · NATIONAL, WHITEHOUSE
Morrison has been on the job for about 15 months, having joined the security council during John Bolton's tenure as national security adviser. Morrison could be a key witness in the inquiry into President Donald Trump's efforts to get Ukraine to investigate his political rivals.
"After more than a year of service at the National Security Council, Mr. Morrison has decided to pursue other opportunities - and has been considering doing so for some time," a senior administration official said in a statement Wednesday. "We wish him well."
Morrison's departure was first reported by NPR.
William Taylor Jr., acting ambassador to Ukraine, testified last week that Morrison told him that Gordon Sondland, the U.S. envoy to the European Union, relayed to a top Ukraine aide that the country wouldn't receive military aid money until the Ukrainian president agreed to pursue an investigation into Joe Biden's son.
To replace Morrison, the White House has hired Andrew Peek, the State Department's deputy assistant secretary of state for Iraq and Iran, said a person familiar with the decision.
Morrison's departure from the National Security Council removes an important vestige of Bolton's tenure in the administration. Bolton handpicked Morrison to join the NSC because of his shared opposition to arms control agreements, which both men view as an unacceptable constraint on American power. Morrison was initially brought on as the senior director for weapons of mass destruction and biodefense.
He is a staunch foe of nuclear nonproliferation advocates who view arms control accords as the only workable means to reducing the risk of nuclear war and managing defense budgets.
During his tenure, Morrison oversaw the U.S. withdrawal from the Reagan-era Intermediate-Range Nuclear Forces and continued to look for ways the U.S. could pull out of other nuclear accords.
This summer, Morrison lobbied Republican offices to urge them not to support an amendment to a defense authorization bill encouraging the administration to extend a landmark nuclear arms reduction treaty known as New START, which expires in February 2021.
In July, Morrison replaced Fiona Hill - who also testified in the impeachment inquiry - as the president's top Russia adviser.
Taylor mentions Morrison's name 15 times in the arresting, 15-page opening statement of his congressional testimony. Morrison told Taylor he had a "sinking feeling" after learning of a conversation between Trump and Sondland, Taylor said. In that exchange, he said, Trump insisted that Ukrainian President Volodymyr Zelensky publicly state he would investigate Biden.
Morrison said he told Bolton and NSC lawyers about the call, according to the testimony.
During another conversation, Taylor said Morrison told him Trump didn't want to provide "any assistance at all" to Ukraine.
"That was extremely troubling to me," Taylor said, adding, "if the policy of strong support for Ukraine were to change, I would have to resign. Based on my call with Mr. Morrison, I was preparing to do so."