MOSCOW — America’s top diplomat in Ukraine, William B. Taylor Jr., described Russia on Wednesday as Ukraine’s “bully neighbor.” Taylor’s remarks during the first open hearing of the impeachment inquiry repeatedly came back to the ongoing conflict between Ukraine and pro-Russian separatists that began in 2014. The war has seen Russia play a shadowy role in provoking and then supporting fighters in two of Ukraine’s eastern regions, including Donbas.

Here’s what happened and where the conflict stands.

Roots in an uprising

The war broke out after a popular uprising in Kyiv sent the corrupt and Kremlin-friendly president, Viktor Yanukovych, into exile across the border in Russia. Russia’s President Vladimir Putin, who takes an exceedingly dim view of popular revolts, feared that Ukraine would leave Russia’s orbit in favor of the European Union. Putin engineered the annexation of the Crimean peninsula, where Russia already had a naval base, and then stoked the uprising in the mostly Russian-speaking Donbas region against the “fascists” who had supposedly taken control in Kyiv.

The separatists are a mixed group. They include local fighters — including some from the ranks of organized crime — and some militiamen from the Russian side. Moscow denies it directly supports the eastern Ukraine units. But Russian aid keeps the fight alive. Last year, a Dutch-led international team of investigators concluded that a missile that downed a Malaysia Airlines jetliner over eastern Ukraine in 2014 came from the Russian military. The attack killed all 298 aboard. Russia denies any link to the disaster.

Low-level fighting continues

More than five years later, the war continues on a low-grade basis. The separatists have not been defeated, but Putin’s backing has driven a wedge between most Ukrainians and Russia that will take generations, perhaps, to heal. The United States and other countries imposed sanctions on Russia, which remain in place, for grabbing Crimea. Under President Barack Obama, the United States provided Ukraine with a limited amount of military materiel and training. President Trump’s delay of about $400 million in military assistance in the summer is at the heart of the impeachment inquiry. But the Trump administration also approved for the first time the sale of Javelin antitank missiles to the Ukrainians.

About 13,000 deaths

About 13,000 people have died in the war, on both sides, and many Ukrainians are weary of it. Potential friends in the European capitals also are getting restless. American diplomats — among them Taylor and George Kent, deputy assistant secretary of state — tried this summer to focus attention on the threat of Russia and the strategic importance of Ukraine to U.S. security. They lobbied strongly for continued security assistance. Both were deeply alarmed by Trump’s attitude toward Ukraine.

Divided opinions over the breakaway region

Opinion is split in Kyiv over whether residents of the separatist regions can ever be successfully reintegrated into Ukrainian society. In the spring, the actor Volodymyr Zelensky, a newcomer to politics, won the presidency in an easy victory, and his supporters later swept control of the parliament. Without getting into specifics, he has talked about finding a way to end the war. Some worry that he is an easy mark for the Kremlin, others that he has been too cozy with right-wing Ukrainian nationalists. Both may have a point.

Cautious overtures for peace

In September, Ukraine and Russia swapped 70 prisoners, and another exchange may be on the way. In October, Zelensky said he was willing to explore a path to peace talks called the Steinmeier Formula. That led to protests in Kyiv against “capitulation.” It has now also brought about a very careful and tentative disengagement in a few towns along the front line. The view among analysts in Ukraine is that Zelensky’s bargaining position with Russia has been weakened by Trump’s attempt to force Ukraine to do his bidding by investigating the Bidens and the country’s supposed role in the 2016 U.S. election. The impeachment inquiry has further driven Zelensky into a tight spot.