What did Donald Trump do today?

He purged yet another staff member who got in his way on Ukraine.

The Senate's final vote not to expel Trump from office was two weeks ago. Since then, Trump has retaliated by firing a number of witnesses who testified about his actions to Congress. These include former ambassador to the E.U. Gordon Sondland and National Security Council Ukraine expert Lt. Col. Alexander Vindman. Trump even fired Vindman's twin brother, Lt. Col. Yevgeny Vindman, who also worked at the NSC but did not take part in the Ukraine investigation.

Today, Trump fired John Rood, the Under Secretary of Defense for Policy he appointed in 2018. Rood did not testify in front of Congress, or publicly speak out about Trump's attempts to force Ukraine to interfere in the 2020 election with a phony "investigation" into Joe Biden. 

But long before the scandal broke publicly, and just hours after Trump gave the order to withhold the desperately needed military aid to the vulnerable government of Ukraine, Rood privately warned Secretary of Defense Mark Esper in an e-mail that Trump was making a mistake and breaking the law. He wrote that "placing a hold on security assistance at this time would jeopardize this unique window of opportunity and undermine our defense priorities with a key partner in the strategic competition with Russia."

Rood was also the Defense Department official who certified that Ukraine was making progress in fighting corruption. This contradicted Trump's later after-the-fact defense that he was calling for a Ukrainian "investigation" into his political rival Joe Biden as an anti-corruption measure.

Rood's e-mail to Esper, along with others from Defense Department officials alarmed by Trump's apparently illegal action, only came to light at the very end of Trump's Senate trial. 

Why is this a problem?

• The only reason for a president to fire someone for pointing out that an order is illegal is if the  president wants the freedom to give more illegal orders.

• Purging anyone who shows the slightest hint of independent thought from the leader is what dictators do.