Russia's President Vladimir Putin has dismissed the armed forces chief, just three days after the defence minister was sacked over a corruption scandal.
Gen Valery Gerasimov replaces Gen Nikolai Makarov as the new armed forces chief of general staff.
Gen Gerasimov commanded Russian forces during the conflict in Chechnya.
Russian authorities are investigating the sale of defence ministry assets at prices below market value.
On Tuesday Mr Putin dismissed defence minister Anatoly Serdyukov, replacing him with a former emergencies minister and loyal ally, Sergei Shoigu.
Mr Shoigu presented Gen Gerasimov to President Putin in the Kremlin on Friday, and described him as "a military man to the roots of his hair".
In their conversation, reported on the Kremlin's official website, Mr Shoigu said the general "has colossal experience, both on the general staff and directly in the field and of course he has battle experience".
Gen Gerasimov was deputy to Gen Makarov for 18 months, in 2010-2012. Most recently he served as commander of Russia's Central Military District.
Russian media report that he served as a commander in the North Caucasus Military District in 1998-2003, during Russia's offensive against separatist rebels in Chechnya.
Mr Putin said Gen Gerasimov would have to tackle problematic relations between the defence ministry and military enterprises.
"Often recently we've come up against changing orders from the defence ministry for industrial suppliers to fulfil... the technology changes rapidly, new means for waging war appear," Mr Putin said.
"Of course, we need to embrace promising new technology, but we also need a certain degree of stability."
Last month, Russian investigators raided the offices of a state-controlled military contractor, Oboronservice, and began investigating the company amid claims that it had sold assets to commercial firms at a loss of nearly 3bn roubles ($95m; £59m).
Oboronservice's activities include servicing military aircraft and arms and constructing military facilities.
Several Oboronservice employees have been arrested and five cases of suspected fraud have been launched by the Russian Federal Investigative Committee. Mr Serdyukov is alleged to have links with the company.
The BBC's Steve Rosenberg in Moscow says the former defence minister had also drawn strong opposition in the military because of his programme to modernise the armed forces, which involved shedding many jobs.
Mr Shoigu has replaced Mr Serdyukov's top aides - the new first deputy defence minister is Arkady Bakhin, former head of the Western Military District, and the new deputy defence minister is Oleg Ostapenko, previously head of the space defence forces.
In February this year Mr Putin announced plans to spend 23tn roubles (£456bn; $729bn) over the next decade on 400 intercontinental ballistic missiles and more than 600 warplanes, as well as nuclear submarines and S-400 missile defence systems.
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