Several senior U.S. diplomats, including former U.S. Ambassador to Ukraine Marie Yovanovitch, are key witnesses in the impeachment inquiry into President Donald Trump. The president is accused of withholding U.S. military aid to Ukraine until that country's new president agreed to investigate one of Trump's political opponents, former Vice President and current presidential candidate Joe Biden. As transcripts from diplomats' closed-door Capitol Hill hearings are released, many are questioning why Secretary of State Mike Pompeo did not shield or support Yovanovitch from an administration campaign that led to her eventual ouster. VOA's diplomatic correspondent Cindy Saine reports from the State Department.