KYIV -- Ukraine's "antiterrorist operation" is officially over. But since the fight against Russia-backed separatists that most Ukrainians know as the "ATO" grinds on, what is still up for debate is: under what name?

With the passage of a contentious reintegration bill by Ukrainian lawmakers on January 17, Kyiv is rebranding the nearly 4-year-old conflict in eastern Ukraine.

Besides defining the vast swath of territory seized by the separatists in Ukraine's eastern regions as "temporarily occupied" by Russia -- a move backers say will help the government restore control over the area and better defend Ukraine's interests in international courts -- the bill puts the Ukrainian army's top command formally in charge of all military and law enforcement activities there, thus formally ending the so-called antiterrorist operation.

The conflict in eastern Ukraine has so far killed more than 10,300 people, including at least eight this month. The central authorities' counteroperations -- often referred to by the snappy acronym "ATO" ("Ah-toh" to Ukrainians) -- were launched by the Ukrainian Security Service (SBU) in April 2014. At the time, Moscow's forced annexation of Crimea was complete and its alleged clients were wresting territory in a mainland Ukraine hobbled by divisive protests and the fresh ouster of a Kremlin-friendly president.

Once the reintegration bill is signed into law by President Petro Poroshenko, the Ukrainian operation will be known -- officially, at least -- by the clunkier "Measures To Ensure National Security And Defense, And Repulsing And Deterring The Armed Aggression Of The Russian Federation In Donetsk And Luhansk Oblasts," for which there does not appear to be a catchy acronym.

Notably, the bill does not state outright that Ukraine is at war with Russia.

When asked on January 19 whether there had been a discussion about what to replace "ATO" with, a Ukrainian official who asked that his name not be used because the issue was not resolved half-jokingly used the Ukrainian abbreviation from the new terminology, "ZZNBO," to describe it.

Confirming the end of the "ATO" to RFE/RL, a presidential spokesman downplayed the name. "More important [is] that the military will now be fully and officially in charge," he added.

Ukraine's Defense Ministry and General Staff of the Armed Forces did not immediately respond to requests for clarity. But a commander who asked that his name not be used because he wasn't authorized to speak for the entire military suggested "Russian aggression" -- a blanket term used frequently by Ukraine's leaders to describe everything from military operations to cyberattacks attributed to Moscow -- "will suit just fine."

Such language has never sat well with Russian officials, who lashed out at Ukraine's passage of a bill that labels Russia "an aggressor state."

"You cannot call this anything but preparation for a new war," the Russian Foreign Ministry said in a statement on January 18, adding that the bill "risked a dangerous escalation in Ukraine with unpredictable consequences for world peace and security."

Rushed Response

Shedding the "ATO" name has been a long time coming.

Kyiv launched the "ATO" under SBU leadership in its rush to respond to the seizure of buildings and territory by armed individuals across Ukraine's Donetsk and Luhansk regions in spring 2014. The separatists involved in that violence were part of what Kyiv and NATO regard as a thoroughly 21st-century approach by Russia dubbed "hybrid warfare."

Underfunded and underprepared due to decades of post-Soviet neglect, Ukraine's military was caught flat-footed at the start of the conflict. In the nearly four years since, however, the Ukrainian armed forces have built themselves into the second-biggest standing army in Europe, with roughly 250,000 active-duty troops and tens of thousands of reservists.

Military instructors have come from the United States, the United Kingdom, Canada, and other Western countries to train Ukrainian troops. Some, including the United States, have given Ukraine's growing army valuable equipment with which to operate.

A Wall Street Journal report citing unnamed U.S. officials suggested that in December U.S. President Donald Trump's administration notified Congress of its intention to supply Kyiv with U.S.-made Javelin antitank missiles. They appeared to be among a range of unspecified measures intended "to deter further aggression," as State Department spokesperson Heather Nauert put it.*

Through it all, the "ATO" name held, and "terrorist" became a part of the Ukrainian lexicon, in an effort to show Moscow and the separatists as the aggressors. Everyone from the president, to soldiers on the front lines, to the national media, to the babushka watching the evening news has uttered the word.

While there have been murmurs about Kyiv wanting to drop it, the first and only real attempt to do so came with the bill passed this week.

But old habits die hard.

The press center for Ukraine's military operation in the east was still using "ATO" in reports and "#ATO" as its profile image on its Facebook page on January 19.

Meanwhile, Balazs Jarabik, a nonresident scholar focusing on Eastern Europe, said he doesn't think the change will be much of an issue among Ukrainians.

"They got 'Russia' instead of 'terrorists,'" Jarabik said.

*CORRECTION: This story has been amended to note that a news report quoted multiple officials asserting that the U.S. administration intended to supply Javelin antitank missiles to Ukraine. There has been no official confirmation of that intention.