That would put the drill below levels that oblige Russian Federation to invite military observers in large numbers from neighbouring states under a treaty called the Vienna Document, with Nato invited to send just three monitors and with a handful of military attaches from Ukraine, Poland, Lithuania, Latvia, Estonia, Sweden, and Norway to also take part. They say Russian Federation could use the occasion to position a large, permanent contingent of troops in Belarus, leaving the country at the mercy of any armed confrontation involving Moscow.
But that has not reassured countries in the region anxious that Russian Federation poses a threat.
NATO's easternmost members have been wary of an increasingly aggressive Russian Federation, particularly following Russia's 2014 military invasion and annexation of Crimea and Moscow's support of separatist rebels in eastern Ukraine.
Get a daily geopolitical forecast.
The US military commander in Europe, Lt General Ben Hodges, echoed such concerns in an interview this summer, admitting that: "people are anxious this is a Trojan horse".
Ukrainian President Petro Poroshenko has stepped up security on his country's border with Belarus, warning that the Zapad (West) 2017 exercises could be a prelude to an invasion.
North Atlantic Treaty Organisation believes the exercises - officially starting on Thursday in Belarus, the Baltic Sea, western Russia and the Russian exclave of Kaliningrad - are already under way. Some NATO members, including the Baltic states and Poland, have criticized a lack of transparency about the exercises and questioned Moscow's real intentions.
"The chiefs of military command centers and the commanders of forces, formations, and military units involved in the drills have received directives from the General Staffs of the Union State's Armed Forces pertaining to the fulfillment of combat training tasks", it said.
In 2014, Russian Federation staged exercises near its border with Ukraine. "President Trump was also briefed about the Russian exercises, Zapad" in which has been anticipated by Western intelligence agencies that 100,000 troops would participate.
Russia, which has the most nuclear warheads in the world, is now working to build up its conventional weapons capabilities to match the U.S., Kofman said.
Moscow says that the drills will involve 12,700 soldiers, 70 aircraft, 250 tanks and ten battleships fighting an imaginary enemy near borders with the Baltic States and Poland. Most notably, Russia's war with Georgia in 2008 and annexation of Crimea in 2014 both followed military exercises that allowed Moscow to move troops into key locations. It also serves to validate aspects of the Ukraine's military training program.
NATO has been critical about how transparent Moscow has been about Zapad 2017, saying it has failed to adhere to worldwide treaties by not allowing observers to monitor the exercise to ensure that it is not a cover for an aggressive military operation.
They are there to emphasise Nato's determination to defend its allies - and Russia's closest Western neighbours. Russian Federation had leased a naval base in Crimea from Ukraine prior to its seizure, and used troops deployed there to quickly take over the Black Sea peninsula.