KIEV — In President Trump’s polarized political universe, there was a “very good” former Ukraine prosecutor on one side and “very bad” people on the other.

But, as is often the case, it’s not that simple.

The former prosecutor in question appears to be Viktor Shokin, 66, who became Ukraine’s prosecutor general in 2015 with promises to wage an unflinching battle against corruption after political upheavals dumped a pro-Russian president and brought in Western-looking leadership.

At the time, it was a message heartily welcomed by major donors such as United States, the European Union and the International Monetary Fund.

Among the companies Shokin said was in his sights: Ukrainian natural gas company named Burisma Holdings. A year earlier, then-Vice President Joe Biden’s son, Hunter, had joined the Burisma board and was also at a law firm retained by Burisma’s owner, former Ukrainian government official Mykola Zlochevsky.

Shokin, however, quickly faced questions of his own. Critics complained that he fell short on his pledges to peer deeply into Ukraine’s shadows.

By the end of his 13-month tenure, Shokin was scorned by the Obama administration and others that had once praised his appointment.

“I heard you had a prosecutor who was very good and he was shut down and that’s really unfair,” Trump told Ukraine’s president, Volodymyr Zelensky, in a July 25 call, according to a rough transcript released Wednesday by the White House. “A lot of people are talking about that, the way they shut your very good prosecutor down and you had some very bad people involved.”

Trump has claimed that Joe Biden in 2015 pressured the Ukrainian government to fire Shokin because he was investigating Burisma.

But the investigation had already been set aside when Biden acted. Yuri Lutsenko, a former Ukrainian prosecutor general who succeeded the fired prosecutor, told Bloomberg News that there was no evidence of wrongdoing by Joe or Hunter Biden.

Shokin was named prosecutor general in February 2015, one year after Viktor Yanukovych, the country’s president at the time, fled the country for Russia following street protests and violent clashes in the capital, Kiev.

Western officials hoped Shokin would aggressively prosecute the extensive corruption — reportedly totaling in the tens of billions of dollars — that authorities uncovered among Yanukovych and his associates.

Public opinion swiftly turned against Shokin, however. He was seen as insufficiently pursuing, and in some instances hindering, cases against the Yanukovych-era officials.

Among these was an investigation into Zlochevsky, Yanukovych’s minister for ecology and natural resources.

In 2014, authorities in Britain froze $23 million linked to Zlochevsky as part of a case against him for alleged money laundering. Shokin’s predecessor, Vitaly Yarema, failed to provide documents requested by British officials, and the money was released in the beginning of 2015.

In September 2015, then-U.S. Ambassador to Ukraine Geoffrey Pyatt gave a speech in which he criticized Shokin for his failure to actively combat corruption.

Calls for Shokin’s dismissal grew through 2015. However, they were resisted by then-President Petro Poroshenko, who had appointed Shokin and with whom he shared a close relationship.

To pressure Poroshenko to dismiss Shokin, the Obama administration threatened to withhold $1 billion in loan guarantees.

In March 2016, Shokin was dismissed.