Alexander Vindman — war hero, European affairs expert, lieutenant colonel in the Army — had lofty dreams of serving the United States. But a call he heard between President Trump and Ukraine’s president, Volodymyr Zelensky, gave him pause. Little more than a year after taking a job at the White House, Colonel Vindman testified before Congress regarding the Ukraine scandal, and was a key witness in the impeachment inquiry into Mr. Trump.

Now retired, citing bullying by the White House, Colonel Vindman tells Kara Swisher he doesn’t regret testifying. But what drew him to the White House in the first place? Why did he speak up when so many others haven’t?

You can find transcripts (posted midday) and more information for all episodes at nytimes.com/sway, and you can find Kara on Twitter @karaswisher.