Russian President Vladimir Putin has ordered the start of the withdrawal of his military from Syria.
During a meeting in the Kremlin with his defence and foreign ministers, Mr Putin said the pullout of forces should start on Tuesday, having largely achieved their aims.
He also ordered the country's diplomatic efforts be stepped up to broker a peace deal in Syria.
The move comes five months after Moscow launched a military operation in support of the Damascus regime.
Waves of airstrikes by Russian warplanes against Syrian opposition forces have reversed the tide of the bloody civil war and put the government of Bashar al Assad on the front foot.
A spokesman said the Russian leader had agreed the move in a telephone call with Mr Assad.
Mr Putin said: "The effective work of our military created the conditions for the start of the peace process.
"I believe that the task put before the defense ministry and Russian armed forces has, on the whole, been fulfilled.
"With the participation of the Russian military... the Syrian armed forces and patriotic Syrian forces have been able to achieve a fundamental turnaround in the fight against international terrorism and have taken the initiative in almost all respects.
"I am therefore ordering the defence minister, from tomorrow (Tuesday), to start the withdrawal of the main part of our military contingent from the Syrian Arab Republic."
However, Moscow will retain a military presence in Syria.
Syria said Moscow had pledged to continue to support the country in "confronting terrorism".
Peace talks
Russia's announcement comes amid fresh peace talks on the conflict, with the UN special envoy for Syria saying if talks fail the "only Plan B available is return to war".
Staffan de Mistura also said that agreeing on a political transition in Syria was the "mother of all issues" at the UN-brokered negotiations in Geneva.
"As far as I know, the only Plan B available is return to war, and to even worse war than we had so far," he said.
He said he would not hesitate to call in the big powers if the talks between the Syrian regime and opposition get bogged down.
"If during these talks and in the next rounds we will see no notice of any willingness to negotiate... we will bring the issue back to those who have influence, and that is the Russian Federation, the USA... and to the Security Council," he told a news conference.
Mr de Mistura said the latest negotiations represented "a moment of truth".
The UN mediator also described a recent ceasefire in the war-torn country as "fragile", but said it had largely held.
The landmark truce signed between the Syrian regime and rebels - but not by jihadist groups like Islamic State and Nusra Front - took effect late last month. A Kremlin spokesman said Russia is hopeful that the talks will have positive results due to the truce.
The US and France at the weekend warned the Damascus regime against trying to disrupt efforts to end the conflict.
Syrian foreign minister Walid Muallem had warned that removing President Bashar al Assad would cross a "red line".
Mr Assad's future has long been a major stumbling block. Syria's key ally Russia rejects any suggestion he should go, while opposition-backer the US is calling for him to step down.
The latest talks are being held on eve of the fifth anniversary of a war which has killed more than 250,000 people, allowed for the expansion of Islamic State and created a growing refugee crisis.
UNICEF has said the conflict has created 2.4 million child refugees and led to children as young as seven being recruited as fighters.
"A trend of particular concern is the increase in child recruitment," the UN charity said in its new report, No Place For Children.
"Children report being actively encouraged to join the war by parties to the conflict offering gifts and 'salaries' of up to $400 a month."
The aid agency GOAL placed an artwork rocket structure Dublin city centre today - to highlight the ongoing suffering of innocent civilians in Syria.
