Officially, just 12,700 soldiers participated, supported by 680 armoured vehicles and 200 artillery systems, a limit under which there is no mandatory declaration to the Organization for Security Cooperation in Europe (OSCE) to send observes to oversee the exercise. Since the end of the Cold War, Western states and Russia agreed on a OSCE document – the Vienna Document  – based on a belief that increases in military transparency (especially when it comes to military exercises) augment security by diminishing the risks of miscalculation and misperception. Yet, since the Russian invasion of Ukraine in 2014, an increased number of military incidents have been registered  across the Euro-Atlantic area (more than 60 between 2014 and 2016), rising tensions and spurring memories of historical analogies: some commentators recalled  the simulated nuclear attack on Warsaw during a previous exercise (Zapad 2009) and the long-standing tradition of using military manoeuvres to hide an impending attack (as occurred in 1968 Czechoslovakia or more recently in the case of Georgia in 2008 and Ukraine in 2014).
The rhetoric coming from Moscow demonstrates how Zapad 2017 – which means “West” in Russian – is meant as a signal that Russian interests are to be taken seriously. From a NATO perspective, as stated  by Secretary General Jens Stoltenberg, the core concern was a lack of transparency, a fact underlined by the invitation of only three experts  from the Alliance to observe the exercise.
The first objective of any military exercise is to assess operational progress. For Zapad 2017, it was the turn of the Western Military District to be placed under scrutiny: how well could its units perform after being the main beneficiaries of the recent transformation of the Russian armed forces? In the past four years, the Western Military District has seen a massive built-up  of forces with the creation of an army headquarters, three army corps, four new divisions and an impressive number of rapid reaction battalions and companies. Zapad brought these new components together to create a coherent force and test its capabilities. In this sense, such manoeuvres represent a normal adaptation and learning cycle, common to the armed forces of any country.
This sabre-rattling cannot be overlooked. Yet, both NATO and the US would do well not to overreact. Obviously, the first thing to avoid is slipping in to an uncontrollable military escalation. Western actors should therefore carefully measure their response. In this respect, and partially overlapping with Russia’s Zapad exercise, Poland and Sweden launched their own military exercises. Cooperating with a large number of nations – seven in the case of Sweden’s Aurora-17  exercise for a total of about 21,000 troops, and 17,000 for Poland’s Dragon-17  coming from nine NATO countries plus Georgia and Ukraine – the two countries sought to demonstrate their own capabilities and strong international backing as a means to deter potential Russian moves.
* Guillaume Lasconjarias is a senior researcher at the NATO Defense College in Rome, where he leads the Transformation chair. Lukáš Dyčka is a researcher at the Centre for Security and Military Strategic Studies, University of Defence, in the Czech Republic, and currently Eisenhower fellow at the NATO Defense College Research Division. The views expressed are the responsibility of the authors and do not necessarily reflect the opinions of the NATO Defense College or the North Atlantic Treaty Organization. A slightly extended Czech version of this article appeared on the website of the NATO Information Center in Prague (natoaktual.cz ) on 2 October 2017.
 See the Vienna Document for specifics: OSCE, Vienna Document 2011 on Confidence- and Security-Building Measures (FSC.DOC/1/11), 30 November 2011, http://www.osce.org/fsc/86597 .
 Łukasz Kulesa, Thomas Frear and Denitsa Raynova, “Managing Hazardous Incidents in the Euro-Atlantic Area: A New Plan of Action”, in ELN Policy Briefs, November 2016, http://www.europeanleadershipnetwork.org/managing-hazardous-incidents-in-the-euro-atlantic-area-a-new-plan-of-action_4211.html .
 See Stephen Blank, “Moscow Pulls Back the Curtain on Zapad 2013”, in Eurasia Daily Monitor, Vol. 10, No. 118 (21 June 2013), https://jamestown.org/?p=18387 .
 NATO, Press point by NATO Secretary General Jens Stoltenberg following the meeting of the NATO-Russia Council, 13 July 2017, http://www.nato.int/cps/en/natohq/opinions_146220.htm ; Daniel Boffey, “NATO Accuses Russia of Blocking Observation of Massive War Game”, in The Guardian, 6 September 2017, https://gu.com/p/76jx8 .
 Andrzej Wilk, “The Zapad-2017 Exercises: The Information War (For Now)”, in OSW Commentaries, No. 249 (1 September 2017), https://www.osw.waw.pl/en/publikacje/osw-commentary/2017-09-04/zapad-2017-exercises-information-war-now .
 See “Militaries Flex Their Muscles in Poland during Dragon-17”, in USA Today, 21 September 2017, https://usat.ly/2wKQVPQ ; and the official Swedish MoD presentation of Aurora-17: http://www.forsvarsmakten.se/en/activities/exercises/aurora-17 .