John Bolton Won't Voluntarily Testify For Impeachment Inquiry

The transcript discusses the potential testimony of John Bolton in the impeachment inquiry. Bolton's lawyer insists on a subpoena for his testimony. House committees have requested Bolton's voluntary appearance, following Fiona Hill's testimony about a rogue operation involving key figures like Rudy Giuliani. The oversight committee, including Representative Ro Khanna, is interested in Bolton's insights on President Trump's knowledge of withholding military aid to Ukraine and other related issues. Bolton was fired by Trump in September due to disagreements on foreign policy.

What three things could Bolton explain according to Representative Ro Khanna?

What led to President Trump firing Bolton?