There’s so much we don’t know about the whistle-blower complaint concerning President Trump. But here are four things we do know:

First, it seems that an experienced intelligence official was so deeply disturbed by Trump’s interactions with the president of Ukraine as to feel the need to blow the whistle.

Second, the inspector general for the intelligence community, Michael Atkinson, who was appointed by Trump and has long experience on national security issues, found the whistle-blower’s concern to be legitimate and urgent.

Third, the whistle-blower complaint came after Trump and his associates hounded Ukraine’s president, Volodymyr Zelensky, to undertake a corruption investigation involving Joe Biden and his son, Hunter. The Ukrainian summary of a July 25 phone call between Trump and Zelensky included this cryptic sentence: “Donald Trump is convinced that the new Ukrainian government will be able to quickly improve image of Ukraine, complete investigation of corruption cases, which inhibited the interaction between Ukraine and the USA.” The Wall Street Journal reports that in that phone call, Trump pressed Zelensky about eight times to work with Trump’s lawyer Rudy Giuliani to investigate the Bidens.

Eight times! Nevertheless, he persisted!

Fourth, Trump withheld $250 million in military assistance urgently needed by Ukraine to fend off Russian aggression, although Ukraine didn’t learn of this until August. He released the money after the whistle-blower complaint and after members of Congress intervened.