Donald Trump doesn’t easily forgive or forget.

As Trump’s Republican allies in the United States Congress block military aid that Ukrainian President Volodymyr Zelenskyy says Kyiv desperately needs to avoid defeat in its war with invading Russian forces, it’s clear the former U.S. president’s ill will toward Ukraine has deep roots.

It was, after all, a phone call with Zelenskyy that led to Trump’s first impeachment in December 2019, after he was accused of seeking to influence the 2020 election by leaning on the Ukrainian leader to investigate current President Joe Biden and his son Hunter.