The inquiry into whether U.S. President Donald Trump abused power to solicit foreign help to discredit a potential adversary in the 2020 presidential election involves a large cast of players.

CGTN’s Gerald Tan walks us through who those key figures are, and how they are all connected.

The impeachment inquiry and Thursday’s proceedings on Capitol Hill center on a telephone call.

On July 25, U.S. President Donald Trump called his Ukrainian counterpart Volodymyr Zelensky. Just days before, Trump had withheld $391 million in military aid to Ukraine.

Part of the half-hour conversation centered on Joe Biden, a leading Democratic candidate seen as Trump’s potential rival for the presidency.

In 2016, Biden, who was then U.S. Vice President, pressured the Ukrainian government to fire its top prosecutor Viktor Shokin on the grounds he wasn’t doing enough to fight corruption.

Shokin’s office was investigating a Ukrainian gas company that appointed Biden’s son, Hunter, to its board of directors. So far, there’s no evidence that Joe Biden’s actions were meant to protect his son’s job.

During the call, Trump repeatedly said that his personal attorney, Rudy Giuliani, and U.S. Attorney-General William Barr would call Zelensky about investigations into the Bidens.

This conversation has come to light because of a U.S. government whistleblower, whose identity has not been released. The official complaint is that Trump was using the power of his office to solicit foreign interference in next year’s presidential election.

As acting U.S. Director of National Intelligence, Joseph Maguire knew of the contents of this complaint but initially withheld it from Congress. He’s now defending his handling of the affair, saying he is neither partisan nor political.

This impeachment inquiry into Trump, however, is almost inevitably partisan and political.