Donald Trump’s replacement for Michael Flynn believes it is imperative for a national security adviser to stand up to the President, otherwise there there could be disastrous consequences.

One consequence was the Vietnam War, during which more than 58,000 Americans and millions of Vietnamese were killed. Lieutenant General H R McMaster wrote a book on the subject, drawing conclusions from the National Security Council and its operations in the 1950s until the 1970s.

In his 1997 book Dereliction of Duty: Lyndon Johnson, Robert McNamara the Joint Chiefs of Staff, and the Lies That Led to Vietnam, he said Americans ended up "questioning the integrity of their government".

He wrote that: "The president was lying, and he expected the Chiefs to lie as well or, at least, to withhold the whole truth. Although the president should not have placed the Chiefs in that position, the flag officers should not have tolerated it when they had."

The shadow of the failed war, he said, hung over the government for decades.

Mr McMaster's advice in the book, according to Politico - and possibly to the new President - is not to lie, do not rely on a close group of advisers and do not attack the media. He accused former President Johnson of being arrogant, weak and self-interested, which led to failings in Vietnam too.

It remains to be seen how Mr McMaster will apply this wisdom to the Trump administration, where the President has frequently attacked the media for being "dishonest" and spreading "fake news", and where he is heavily reliant on a group of advisers including Stephen Bannon and Stephen Miller.

New York City bodegas strike to protest Trump's travel ban Show all 27 1 /27 New York City bodegas strike to protest Trump's travel ban New York City bodegas strike to protest Trump's travel ban Ethnic Yemenis and supporters protest against President Donald Trump's executive order temporarily banning immigrants and refugees from seven Muslim-majority countries, including Yemen on February 2, 2017 in the Brooklyn borough of New York City. At least 1,000 Yemeni-owned bodegas and grocery-stores across the city shut down from noon to 8 p.m. today to protest the order. Spencer Platt/Getty New York City bodegas strike to protest Trump's travel ban People rally at Brooklyn Borough Hall as Yemeni bodega and grocery-stores shut down to protest US President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen, on February 2, 2017 in New York. Bryan R. Smith/AFP/Getty New York City bodegas strike to protest Trump's travel ban Men pray during a protest by ethnic Yemenis and supporters over President Donald Trump's executive order temporarily banning immigrants and refugees from seven Muslim-majority countries, including Yemen on February 2, 2017 in the Brooklyn borough of New York City. At least 1,000 Yemeni-owned bodegas and grocery-stores across the city shut down from noon to 8 p.m. today to protest the order. Spencer Platt/Getty New York City bodegas strike to protest Trump's travel ban Ethnic Yemenis and supporters protest against President Donald Trump's executive order temporarily banning immigrants and refugees from seven Muslim-majority countries, including Yemen on February 2, 2017 in the Brooklyn borough of New York City. At least 1,000 Yemeni-owned bodegas and grocery-stores across the city shut down from noon to 8 p.m. today to protest the order. Spencer Platt/Getty New York City bodegas strike to protest Trump's travel ban Men pray during a protest by ethnic Yemenis and supporters over President Donald Trump's executive order temporarily banning immigrants and refugees from seven Muslim-majority countries, including Yemen on February 2, 2017 in the Brooklyn borough of New York City. At least 1,000 Yemeni-owned bodegas and grocery-stores across the city shut down from noon to 8 p.m. today to protest the order. Spencer Platt/Getty New York City bodegas strike to protest Trump's travel ban People rally at Brooklyn Borough Hall as Yemeni bodega and grocery-stores shut down to protest US President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen, on February 2, 2017 in New York. Spencer Platt/Getty New York City bodegas strike to protest Trump's travel ban People rally at Brooklyn Borough Hall as Yemeni bodega and grocery-stores shut down to protest US President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen, on February 2, 2017 in New York. Bryan R. Smith/AFP/Getty New York City bodegas strike to protest Trump's travel ban People rally at Brooklyn Borough Hall as Yemeni bodega and grocery-stores shut down to protest US President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen, on February 2, 2017 in New York. Spencer Platt/Getty New York City bodegas strike to protest Trump's travel ban People rally at Brooklyn Borough Hall as Yemeni bodega and grocery-stores shut down to protest US President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen, on February 2, 2017 in New York. Spencer Platt/Getty New York City bodegas strike to protest Trump's travel ban People gather for evening prayer at a rally at Brooklyn Borough Hall as Yemeni bodega and grocery-stores shut down to protest US President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen, on February 2, 2017 in New York. Bryan R. Smith/AFP/Getty New York City bodegas strike to protest Trump's travel ban People rally at Brooklyn Borough Hall as Yemeni bodega and grocery-stores shut down to protest US President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen, on February 2, 2017 in New York. Bryan R. Smith/AFP/Getty New York City bodegas strike to protest Trump's travel ban People rally with flags at Brooklyn Borough Hall as Yemeni bodega and grocery-stores shut down to protest US President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen, on February 2, 2017 in New York. Bryan R. Smith/AFP/Getty New York City bodegas strike to protest Trump's travel ban People rally at Brooklyn Borough Hall as Yemeni bodega and grocery-stores shut down to protest US President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen, on February 2, 2017 in New York. Spencer Platt/Getty New York City bodegas strike to protest Trump's travel ban People rally at Brooklyn Borough Hall as Yemeni bodega and grocery-stores shut down to protest US President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen, on February 2, 2017 in New York. Spencer Platt/Getty New York City bodegas strike to protest Trump's travel ban People rally at Brooklyn Borough Hall as Yemeni bodega and grocery-stores shut down to protest US President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen, on February 2, 2017 in New York. Spencer Platt/Getty New York City bodegas strike to protest Trump's travel ban People rally at Brooklyn Borough Hall as Yemeni bodega and grocery-stores shut down to protest US President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen, on February 2, 2017 in New York. Spencer Platt/Getty New York City bodegas strike to protest Trump's travel ban People rally at Brooklyn Borough Hall as Yemeni bodega and grocery-stores shut down to protest US President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen, on February 2, 2017 in New York. Spencer Platt/Getty New York City bodegas strike to protest Trump's travel ban People rally with flags at Brooklyn Borough Hall as Yemeni bodega and grocery-stores shut down to protest US President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen, on February 2, 2017 in New York. Bryan R. Smith/AFP/Getty New York City bodegas strike to protest Trump's travel ban People rally with flags at Brooklyn Borough Hall as Yemeni bodega and grocery-stores shut down to protest US President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen, on February 2, 2017 in New York. Bryan R. Smith/AFP/Getty New York City bodegas strike to protest Trump's travel ban People rally with flags at Brooklyn Borough Hall as Yemeni bodega and grocery-stores shut down to protest US President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen, on February 2, 2017 in New York. Bryan R. Smith/AFP/Getty New York City bodegas strike to protest Trump's travel ban People rally at Brooklyn Borough Hall as Yemeni bodega and grocery-stores shut down to protest US President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen, on February 2, 2017 in New York. Bryan R. Smith/AFP/Getty New York City bodegas strike to protest Trump's travel ban People rally with flags at Brooklyn Borough Hall as Yemeni bodega and grocery-stores shut down to protest US President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen, on February 2, 2017 in New York. Bryan R. Smith/AFP/Getty New York City bodegas strike to protest Trump's travel ban People rally at Brooklyn Borough Hall as Yemeni bodega and grocery-stores shut down to protest President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen, on February 2, 2017 in New York. Bryan R. Smith/AFP/Getty New York City bodegas strike to protest Trump's travel ban A Yemeni business owner places a sign on the gate of his store February 2, 2017 in the Brooklyn borough of New York City. Across the city, Yemeni owned bodega and grocery-stores will shut down from noon to 8 p.m. to protest President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen. It is expected that over 1000 stores will be closed in protest with workers and owners participating in an afternoon rally in Brooklyn. Spencer Platt/Getty New York City bodegas strike to protest Trump's travel ban A Yemeni business owner places a sign on the gate of his store February 2, 2017 in the Brooklyn borough of New York City. Across the city, Yemeni owned bodega and grocery-stores will shut down from noon to 8 p.m. to protest President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen. It is expected that over 1000 stores will be closed in protest with workers and owners participating in an afternoon rally in Brooklyn. Spencer Platt/Getty New York City bodegas strike to protest Trump's travel ban NEW YORK, NY - FEBRUARY 02: Yemeni business owner Musa closes the gate to his store February 2, 2017 in the Brooklyn borough of New York City. Across the city, Yemeni owned bodega and grocery-stores will shut down from noon to 8 p.m. to protest President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen. It is expected that over 1000 stores will be closed in protest with workers and owners participating in an afternoon rally in Brooklyn. Spencer Platt/Getty New York City bodegas strike to protest Trump's travel ban A Yemeni business owner closes the gate to his store February 2, 2017 in the Brooklyn borough of New York City. Across the city, Yemeni owned bodega and grocery-stores will shut down from noon to 8 p.m. to protest President Donald Trump's Executive Order banning immigrants and refugees from seven Muslim-majority countries, including Yemen. It is expected that over 1000 stores will be closed in protest with workers and owners participating in an afternoon rally in Brooklyn. Spencer Platt/Getty

James Jeffrey, a top diplomat, a former deputy National Security Adviser under George W Bush and who worked with Mr McMaster in Iraq in 2005, told The Independent that the new appointee would speak his mind.

"I’m pretty optimistic concerning him. The main thing is he’s a blunt, outspoken guy and he’s self-confident," he said.

Mr Jeffrey stressed that the National Security Adviser has no power to execute a plan without the President’s permission.

"As National Security Adviser you’re the President’s staffer and your job is to give him the best advice possible but at the end of the day the President makes a decision and you execute it. You co-ordinate it, monitor it, but you have no real execution authority yourself."

"His best possible advice may run contrary to what the President indicates."

Mr McMaster will be present for the delivery of the President’s Daily Briefing on security matters and global threats. If there are warnings in the briefing, they will not go unnoticed because the document is read by many people, added Mr Jeffrey.

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But, similar to the Vietnam War era, the number of National Security Council’s principals committee staff has been reduced and the power of the Joint Chiefs of Staff has become more limited.

The purpose of the meetings, mostly composed of civilian analysts and lawyers, was to expand the consensus for decisions already made.

Mr Trump appointed Breitbart founder Mr Bannon to become a permanent member of the NSC. The President issued a directive in January to ensure that the Director of National Intelligence and Chairman of the Joint Chief of Staffs should only attend the committee meetings "where issues pertaining to their responsibilities and expertise are to be discussed".

"Bannon has a desire to create chaos which is a bigger danger to the Republic than his actual political agenda," said Mr Jeffrey, "which is far too nationalistic and focuses on repairing economic problems that no one can fix and is, on the margins, extremely intolerant."