By Guy Faulconbridge
MOSCOW Russian President Vladimir Putin in March announced a plan to deploy tactical nuclear weapons in Belarus, Moscow's first move of such warheads outside Russia since the 1991 fall of the Soviet Union.
What is known about the deployment?
WHAT DID PUTIN SAY?
Putin's nuclear deployment is a message to the West that he will not back down over the Ukraine war.
Putin made the announcement, almost as an afterthought, in an interview with state television Kremlin correspondent Pavel Zarubin that was first posted on Telegram on March 25.
Putin said the trigger for the decision to deploy in Belarus was an announcement by Britain that it would supply depleted uranium munitions to Ukraine. The Wall Street Journal reported on June 13 that the United States was also set to approve depleted uranium tank rounds for Ukraine.
Belarus said the deployment was in answer to the West's "aggressive policy" and that it was aimed at forcing the West's leaders to think before escalating.
WHAT WEAPONS WILL BE DEPLOYED AND WHERE?
Putin said that "tactical" nuclear weapons - so called as they are designed for battlefield use - would be sent to Belarus but did not say exactly which warheads would be deployed or where.
Lukashenko said the warheads are three times more powerful than the atomic bombs the United States dropped on the Japanese cities of Hiroshima and Nagasaki in August 1945.
The Hiroshima bomb, made from highly enriched Uranium-235, was about 16 kilotons (equivalent to 16,000 tonnes of TNT), while the Nagasaki bomb, made from plutonium-239, was about 21 kilotons, according to the World Nuclear Association.
If Lukashenko is correct, the Russian warheads would have a yield of about 48 to 63 kilotons each. Russia has about 1,816 non-strategic nuclear warheads, according to a Bulletin of Atomic Scientists' analysis of Russia's nuclear weapons.
Putin said Iskander mobile short-range ballistic missiles, which can deliver nuclear warheads, had already been handed over to Belarus. Russian sources say the Iskander has a range of 500 km (310 miles).
Putin also said 10 Belarusian aircraft had been adapted to carry the warheads. Belarus said Su-25 aircraft had been adapted to carry the warheads. The Sukhoi-25 jet has a range of up to 1,000 km (621 miles), according to Russian sources.
The Federation of American Scientists has said the weapons could be based at Lida air base, 40 km (25 miles) from the Lithuanian border.
If so, the delivery vehicles could potentially reach most of Ukraine, almost all of eastern Europe, including the Baltic states, Poland, Slovakia, Hungary, Czech Republic, Romania, a swathe of Germany, as well as some of Denmark, Sweden and Finland. Cities such as Berlin and Stockholm would be in range.
WHEN?
Putin said Russia would finish the construction of a special storage facility in Belarus on July 7-8 and the weapons would be deployed soon afterwards.
Lukashenko has made different comments. He seemed to indicate last month that the weapons were already on the move while on June 13 he said the weapons would be deployed in "several days".
He has also said that there could be "nuclear weapons for everyone" who joined the Russia-Belarus union. In a video published on June 14, Lukashenko has said his country had started taking delivery of Russian tactical nuclear weapons
WHO CONTROLS THEM?
Putin said Russia would remain in control of the weapons just as the United States controls its own tactical nuclear weapons deployed in Europe.
The United States has had nuclear weapons deployed in Europe since the 1950s at NATO bases.
Putin has repeatedly raised concerns about the 200 U.S. B61 tactical nuclear warheads deployed at bases in Belgium, the Netherlands, Germany, Italy and Turkey.
Those U.S. warheads are kept in vaults at air bases and the United States keeps the Permissive Action Link (PAL) codes used to arm them.
Russia's nuclear weapons are controlled and transported by the 12th Main Directorate of the defence ministry (12th GUMO).
NUCLEAR RISKS?
After the Soviet Union collapsed in 1991, the United States went to enormous lengths to ensure that the Soviet nuclear weapons stationed in Belarus, Ukraine and Kazakhstan were returned to Russia - which inherited the Soviet nuclear arsenal.
By putting nuclear weapons back in Belarus, Putin is showing that the architecture of post-Cold War nuclear arms control is crumbling.
WHAT IS THE U.S./NATO RESPONSE?
The United States has criticised Putin's nuclear deployment but has said it has no intention of altering its posture on strategic nuclear weapons and also that it has not seen any signs Russia is preparing to use a nuclear weapon.
The State Department said on March 27 that speaking candidly, it condemned the announcement of the deployment. NATO Secretary General Jens Stoltenberg said on April 18 that Putin's decision was irresponsible.
(Reporting by Guy Faulconbridge; Editing by Nick Macfie, Robert Birsel)