Oleksandr Turchynov, head of Ukraine's National Security and Defense Council, has issued a statement outlining the structure of the military forces of the Russia-backed separatists fighting in eastern Ukraine.

"Russia has completed the creation of a powerful ground formation, based on two army corps, ready to conduct active offensive operations," the statement released on August 27 reads. "Key command and staff positions in these army corps are occupied by Russian staff officers."

The force is largely made up of local enlistees and "contract soldiers and mercenaries from Russia," the report claims, and has an authorized strength of up to 35,000 men.

The same day, Aleksandr Borodai, the former self-proclaimed prime minister of the unrecognized Donetsk People's Republic (DNR), said between 30,000 and 50,000 "Russian volunteers" had fought in eastern Ukraine over the last year.

Moscow insists that its military is not involved in the Ukraine conflict and that any Russian citizens fighting there are civilians.

Turchnyov's statement also names four active Russian generals it says are playing key roles in the military organization of the separatists. One of them, Major General Aleksei Zavizion, was included on a list of five Russian generals working in Ukraine that was released by the Ukrainian Security Service (SBU) in July.

This brings the total number of active Russian generals that Ukrainian security officials have named as being in command positions of the separatist military forces in eastern Ukraine to eight.

RFE/RL takes a closer look at the officers who have been implicated:

​ Colonel General Andrei Serdyukov

Turchynov said on August 27 that Serdyukov is carrying out "the command of all the grouping of Russian occupation forces," using the code name "Sedov."

According to most sources, Serdyukov, 53, was born and raised in the town of Ambrosiivka in Ukraine's Donetsk Oblast, on the very border with Russia. Other sources say he was born in Russia's Rostov Oblast.

After completing school, he enrolled in the paratrooper academy in Ryazan in 1979. In the 1990s, he spent one year as deputy commander of Russian peacekeeping forces in Kosovo. He served two one-year rotations in Chechnya. In 2013, he became chief of staff and first deputy commander of the Southern Military District based in Rostov-on-Don.

As a colonel general, the equivalent of a U.S. three-star general, Serdyukov is the highest-ranking officer named by Ukraine as participating in the war.

​ Major General Yevgeny Nikiforov

Turchynov said that Nikiforov is the commander of the 2nd Army Corps in eastern Ukraine and is operating under the code name "Morgun." Other sources say that he is using the code name "Tambov," which he purportedly inherited from his predecessor in Ukraine, Major General Sergei Kuzovlyov (see below).

According to the Ukrainian website Informnapalm.org, Nikiforov completed the Kolomenskoye Artillery Academy in 1991. He became a brigade commander in 2005.

He is currently the deputy commander of the 58th Army of the Southern Military District, a unit that participated in the 2008 war in Georgia.

Lieutenant General Sergei Yudin

Turchynov claimed that Yudin formerly commanded the 2nd Army Corps before being recently rotated out and replaced by Nikiforov.

Yudin was reportedly born in Baku in 1959 and performed his military service with the Soviet Red Army in the Transcarpathia region of western Ukraine. He later enrolled in a military academy, from which he graduated in 1984. He served with Soviet forces in Germany before being transferred to the Russian Far East.

He graduated from the Frunze Military Academy in Moscow in 1993. He served in the first Chechen war from 1994 to 1996 as a brigade chief of staff. He returned to combat in Chechnya in 1999 during the second Chechnya war.

He graduated from the Academy of the General Staff, also in Moscow, in 2004. From 2004-06 he commanded the Russian forces in Tajikistan.

Major General Oleg Tsekov

Tsekov graduated from a military institute in Chelyabinsk in 1988. He then served in various parts of the Soviet Union and Mongolia.

He graduated from the Academy of the General Staff in 2011. The same year, he was appointed commander of the 200th motorized special-forces brigade of the Northern Fleet. In September 2014, the volunteer information service InformNapalm published evidence that the unit had been mobilized from Murmansk Oblast to Rostov Oblast, together with evidence that service personnel from the 200th had been identified in Ukraine.

Tsekov was promoted to major general on February 21, 2015.

The July SBU dossier charges that Tsekov commands the so-called 2nd brigade of the separatist forces near Donetsk.

​ Major General Valery Solodchuk

Born in Astrakhan, Solodchuk graduated from the paratroops institute in Ryazan in 1992. In 2012, he was named commander of the 7th guards air-assault division based in Novorossiisk. A media reference in 2014 identified Solodchuk as deputy commander of the 5th Army in the Far East.

Digital-forensic investigators have drawn attention to a soldier of the 7th guards air-assault division named Stanislav Ramensky. He posted on social media several photographs that seem to have been taken in Crimea in March 2014, when Russia annexed the peninsula from Ukraine. He also published a photograph of the medal and certificate he was given on April 14, 2014, "for the return of Crimea," which was signed by Solodchuk.

In an interview with the Russian-government newspaper Rossiiskaya Gazeta in March, Solodchuk was asked if the 7th guards air-assault division is a designated rapid-reaction unit within the Russian military. He answered that there are no such units and that the entire military is in a state of constant combat readiness. Asked if that meant that his unit is prepared to be ordered into battle at any moment, Solodchuk answered, "Exactly."

The SBU dossier charges that Solodchuk is the commander of so-called 1st Army Corps of Novorossia in the Donetsk area.

​ Major General Sergei Kuzovlyov

Sergei Kuzovlyov was born in 1967 and graduated from the paratroops institute in Ryazan in 1990. He also studied at the Academy of the General Staff. He was promoted to major general in February 2014. Since 2014, he has been chief of staff of the 58th Army based in Vladikavkaz.

In January, the Ukrainian SBU released an audio recording that it alleged showed Kuzovlyov organizing the military forces of the self-proclaimed Luhansk People's Republic in eastern Ukraine. The SBU says Kuzovlyov goes by the pseudonyms "Tambov" and "Ignatov."

​ Major General Aleksei Zavizion

Aleksei Zavizion was born in Narva, Estonia, in 1965 and graduated from a military institute in Chelyabinsk in 1986. He served in the Far East, in Chechnya, and as commander of Russian forces in Tajikistan.

In 2009, he began studies at the Academy of the General Staff.

In March, Ukraine's SBU claimed Zavizion, using the nom de guerre Alagir, directed the shelling of Kramatorsk and Mariupol. Referring to Zavizion, SBU official Markiian Lubkivskyi wrote on Facebook that "a citizen of the Russian Federation...with the call sign Alagir is currently in Donetsk within the rotational assignment of running the Operational Headquarters since January 2015, coordinating military operations with the participation of representatives of illegal armed formations."

"Alagir is the person in charge of the deployment of artillery, mobile rocket systems, and heavy equipment," Lubkivskyi continued. "Major bloody attacks on Ukrainian cities, particularly on Kramatorsk and Mariupol, were carried out under his direct command and coordination."

Lubkivskyi also wrote that Zavizion was scheduled to be replaced by Russian Major General Andrei Gurulyov.

Major General Roman Shadrin

Roman Shadrin was born in Rostov Oblast in 1967 and graduated from a military institute in Kazan. He served in the Soviet contingent in East Germany after graduating in 1988. In 1995, he was awarded the Hero of Russia medal for his service during the first war in Chechnya. After service in Armenia and the North Caucasus, Shadrin was named deputy commander of Interior Ministry troops in the Urals region. In 2008, he served during the conflict with Georgia in the breakaway Georgian region of South Ossetia, after which he was promoted to major general.

In September 2013, he was elected to the Yekaterinburg City Duma from the ruling United Russia Party.

The SBU dossier says Shadrin is the so-called minister of state security for the self-proclaimed "Luhansk Peoples Republic" (LNR) in eastern Ukraine. According to a media report on July 3, Shadrin denies the allegation, saying he has only traveled to Ukraine's Donbas region "with a humanitarian mission."

The Yekaterinburg-based Novy Den news agency reported the same day that Shadrin has "repeatedly traveled to eastern Ukraine with humanitarian missions." It also noted that Shadrin resigned as chairman of the city legislature's security committee in January and quoted an unidentified source in the Yekaterinburg Duma as saying Shadrin "holds one of the top positions in the security service of the LNR."

The same source said it is not known when Shadrin will return to his duties in Yekaterinburg, but there have been no efforts to strip him of his mandate.