British Defense Secretary Michael Fallon has said Russia's upcoming military maneuvers with Belarus are aimed at "provoking" NATO and "testing" its defenses.
"Russia is testing us and testing us now at every opportunity," Fallon said on the BBC’s Andrew Marr Show on September 10. "We’re seeing a more aggressive Russia. We have to deal with that."
Under Organization for Security and Cooperation in Europe (OSCE) rules known as the Vienna Document, states conducting maneuvers involving more than 13,000 troops must notify other nations in advance and be open to observers.
Russia and Belarus say the Zapad (West) 2017 exercises, which are set to be held in Belarus and parts of western Russia on September 14-20, will involve about 12,700 troops.
But Western military officials and experts say that the true numbers could be far higher, with as many as 100,000 military personnel involved.
Russia charges that Western concerns about the exercises are unfounded, saying the war games will be defensive and pose no threat to Russia's neighbors, NATO, or the West.
"This is [Russia’s] biggest exercise I think for four years -- over 100,000 Russian and Belarusian troops ... on NATO’s borders," Fallon said. "This is designed to provoke us, it’s designed to test our defenses, and that’s why we have to be strong.”
NATO says it will send three observers to Belarus and Russia to monitor Zapad 2017, but it has repeatedly called on the two countries to allow broader monitoring of the drills.
The alliance’s secretary-general, Jens Stoltenberg, called on Russia to be "fully transparent," telling the BBC on September 10 that Russia has a history of "under-reporting" the number of troops in its exercises and "using loopholes in international agreements to avoid international observation."
"We have seen before that Russia has used big military exercises as a disguise or a precursor for aggressive military actions against their neighbors," Stoltenberg also said. "That happened in Georgia in 2008 when they invaded Georgia, and it happened in Crimea in 2014 when they illegally annexed [Ukraine’s] Crimea [region]."
Speaking on September 7 in the Estonian capital, Tallinn, the French and German defense ministers condemned the Zapad 2017 exercises, saying Moscow is seeking to show off military might on the borders of the EU and NATO.
"It is particularly important in this context that we reaffirm our presence in the face of...this demonstration the Russians are making which is a strategy of intimidation," France's Defense Minister Florence Parly said.
"It is undisputed that we see a demonstration of capabilities and power of the Russians," German Defense Minister Ursula von der Leyen said. "Anyone who doubts that only has to look at the high numbers of the participating forces in the Zapad exercise: more than 100,000."
The Russian Defense Ministry said on September 9 that it was "bewildered by the statements of Ursula von der Leyen, publicly talking through her hat and making arbitrary allegations about 100,000 Russian troops ...and about hidden threats to Europe."
On September 7, the ministry said that Russia’s Armed Forces General Staff chief Valery Gerasimov used a meeting in Azerbaijan with the chairman of the NATO military committee, Petr Pavel, to reassure him about the war games.
Gerasimov told Pavel that the joint exercises with Belarus were "long-planned and defensive" and "not aimed against any third country," a statement carried by Russian news agencies said.
NATO said the September 7 meeting in Baku "demonstrates a clear mutual interest to maintain the military lines of communication," but did not give any details on what was discussed.
Russia holds the Zapad exercises every four years, rotating them with drills in three other parts of the country.
Belarus borders NATO members Poland, Lithuania, and Latvia, as well as Ukraine. The area the upcoming exercises are due to take place also includes the Russian exclave of Kaliningrad, which lies between Poland and Lithuania on the Baltic Sea.
Russia's military actions in Ukraine have increased concerns about Moscow's intentions in NATO nations, particularly former Soviet republics or Warsaw Pact satellites of the Soviet Union.
Russia occupied and seized the Crimean Peninsula in March 2014 and backs separatists whose war against Kyiv's forces has killed more than 10,000 people in eastern Ukraine since April of that year.
Those actions have prompted NATO to step up its defenses in the east, deploying four multinational battle-groups in the three Baltic states and Poland -- totaling approximately 4,500 troops.