NATO: Article V and Collective Defense
CRS Report for Congress
NATO: Article V and Collective Defense
Paul E. Gallis
Specialist in European Affairs
Foreign Affairs and National Defense Division
Article V of the North Atlantic Treaty does not guarantee the use of force to assist
an ally under attack. Nonetheless, the U.S. pledge of collective defense has been the core
of the alliance. NATO views collective defense, and not collective security, as its core
function. This study will not be updated.
A collective security organization settles disputes among its members. In contrast,
a collective defense organization assists a member state under attack by an outside country.
NATO is a collective defense organization. Article V states that NATO members must
consider coming to the aid of an ally under attack. However, it does not guarantee
assistance. Article V is the Treaty's key provision and the linchpin binding the United States
to its NATO allies. It states, in part, that "an armed attack against one or more [allies] shall
be considered an attack against them all." Additional language makes clear that the
commitment to assist an ally is not unconditional. Rather, each signatory will assist the ally
under attack with "such action it deems necessary, including the use of armed force...."1
Since the early 1990s, NATO has begun to adopt "new missions," such as crisis management
and peacekeeping, sometimes referred to as "non-Article V missions." Current members
and candidate states, however, believe collective defense, as expressed in Article V, remains
the core of the alliance, a view likely to endure as long as the possibility of a nationalistic,
aggressive Russia remains.
Article V states, in full: "The Parties agree that an armed attack against one or more of them in1
Europe or North America shall be considered an attack against them all and consequently they agree
that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective
self-defense recognized by Article 51 of the Charter of the United Nations, will assist the Party or
Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action
as it deems necessary, including the use of armed force, to restore and maintain the security of the
North Atlantic area.
Any such armed attack and all measures taken as a result thereof shall immediately be reported
to the [UN] Security Council. Such measures shall be terminated when the Security Council has
taken the measures necessary to restore and maintain international peace and security."
Congressional Research Service ˜ The Library of Congress
Collective Security: Precursor to Collective Defense
Congress was reluctant to engage the United States in either World War. In each
conflict, strong presidential advocacy and growing threats to broader U.S. interests led to
eventual involvement. After World War I, the U.S. Senate voted down the Versailles Treaty
and, with it, involvement in the League of Nations because opposition remained strong to
"entangling alliances". The protection offered by the Atlantic and Pacific Oceans contributed
to the view that the United States still enjoyed a relatively unbridgeable barrier against attack.
The League of Nations Covenant, embedded in the Versailles Treaty, allowed but did
not require signatories to use military force and economic sanctions against an aggressor.
The League embodied the idea of "collective security," under which an international
organization might seek to settle disputes among its members. President Wilson and other
League supporters emphasized "the condemnation of public opinion" and "moral force"
as key instruments in international affairs. Hitler's manipulation of public opinion and his
intimidation of neighboring states made a mockery of such notions. Churchill, who urged
military force against Germany from the early 1930s, taunted supporters of collective security
and the League as guilty of "long-suffering and inexhaustible gullibility." U.S. absence from2
the League left the institution without the strongest economic and military power after
World War I, and therefore without effective leadership.
Collective Defense: Evolution of an Idea
The global depression of the 1930s and the Second World War made clear that events
in Europe greatly affected U.S. economic and political interests. From a desire to bring
global stability, there was considerable support in Congress for creation of the United Nations
in 1945. Article 1 of the UN Charter outlined a resolve "to maintain international peace
and security, and... take effective collective measures for the prevention and removal of
threats to the peace, and for the suppression of acts of aggression." Article 51 stated the
"inherent right of individual or collective self-defense if an armed attack occurs...." A
unanimous vote in the Security Council was necessary for a collective response, and the
Soviet Union blocked meaningful UN action in the early years.
In the late 1940s, continuing instability in Europe led Congress and President Truman
to move towards clear engagement in European security. The Soviet Union's blockade of
Berlin, a Soviet-backed coup in Czechoslovakia, and a civil war in Greece with communists
pitted against a democratic government were key events arousing U.S. efforts to construct
a security edifice.
In 1948, Sen. Vandenberg, previously an isolationist, sponsored a resolution stating
that the United States should pursue the "progressive development of regional and other
collective defense arrangements for individual and collective self-defense" in accordance
with the UN Charter. The Senate Foreign Relations Committee approved the resolution,
which passed, and issued a report on the proposed North Atlantic Treaty that strongly
For a contemporary view, see E.H. Carr, The Twenty Years' Crisis, 1919-39, (New York, 1939).2
endorsed collective defense. The Senate approved the Treaty, which went into force August
The Foreign Relations Committee report recommended "U.S. association with
arrangements for collective defense" but laid down three conditions for U.S. involvement.
First, U.S. contributions to collective defense "must supplement, rather than replace, the
efforts of the other participants on their behalf." This condition, frequently noted in Senate
debate in succeeding years, meant that allies must contribute significant forces to their own
defense, so that the United States would not bear the brunt of the burden. Second, a
President must follow "constitutional processes" for the United States to become involved
in any security arrangement or conflict, a signal that the Senate wished to exercise its duty
to give advice and consent to defense arrangements that might commit U.S. forces to war.
Third, for the United States to fulfill a collective defense commitment, U.S. national interests
must clearly be affected.4
From NATO's early days, the role and size of U.S. forces in Europe were keys to
ensuring the viability of Article V. Only small contingents of U.S. conventional forces were
in Europe at NATO's origins in 1949. The outbreak of the Korean War in 1950 and western
Europe's continuing economic weakness and political instability led President Truman to
send more U.S. forces to the continent. In the early 1950s, there was strong opposition
in Congress to the policy of sending large-scale U.S. forces to Europe, given the long-
expressed sentiment that the United States should "supplement, rather than replace" allied
forces. Presidents Truman and Eisenhower eventually prevailed in their desire to maintain
a sizeable U.S. force in the European theater. U.S. officials, seeing a growing Soviet threat,
desired a contribution of West German economic and military potential to the alliance. West
Germany joined the alliance in 1955.
Nuclear Weapons and "Flexible Response"
The development of nuclear arsenals by both the United States and the Soviet Union
complicated the debate over collective defense from the 1950s through the end of the Cold
War. Through the mid-1950s, the United States had a larger and more sophisticated nuclear
arsenal than the Soviet Union, while the Warsaw Pact was thought to maintain conventional
superiority. However, by 1960, the Soviets' successful space program and their development
of a large bomber fleet and missile force clearly signalled that the continental United States
was vulnerable to nuclear attack in any conflict originating in Europe. The European allies
sought reassurances that the United States "would trade Washington for Moscow" if war
again came to Europe.
In 1967, under U.S. leadership, the alliance formulated the doctrine of "flexible
response," by which NATO would use whatever means necessary to deter or repel a Soviet
attack. Conventional forces would be initially engaged, but the United States pledged that
it would use its strategic nuclear arsenal to defeat the Warsaw Pact if conventional forces
failed in the defense of western Europe. Succeeding U.S. administrations and Congress
consistently urged the allies to increase their conventional forces as the principal means to
See North Atlantic Treaty, Senate Foreign Relations Committee Report. 81st Congress, 1st sess.3
Washington, June 6, 1949.
Ibid., p. 78.4
defeat a Soviet attack and avoid the calamity of a nuclear conflict. In 1978, for example,
the alliance agreed upon a non-binding pledge to increase defense spending by 3% a year
in order to strengthen conventional forces; this commitment was only irregularly met by
the allies. Several factors contributed to the Europeans' failure to strengthen their
conventional forces: the presence of significant political groupings that viewed increased
defense expenditures as provocative in an already tense international atmosphere; economic
strictures; and the stationing, by 1980, of over 300,000 U.S. forces that carried a significant
part of the burden. Conventional forces were expensive to maintain, and nuclear forces
were relatively inexpensive. Both France and Britain had nuclear arsenals, which their
political leaders believed contributed to deterrence.
Some observers continue to believe that "flexible response" was essentially a myth.
In the view of one prominent analyst, "the attempt to deter conventional aggression in
Europe with a nuclear arsenal controlled by a non-European power [the United States] that
is itself subject to nuclear retaliation has never appeared to be an example of political or
military rationality." Nonetheless, in the view of many strategists, the U.S. threat to use5
nuclear weapons served to create sufficient doubt in the minds of Soviet leaders to deter
an attack. The United States deployed some of its nuclear weapons in forward areas, such
as West German territory, to signal the Warsaw Pact that they might be used early in a
conflict. The presence of significant U.S. conventional forces was itself a component of
the philosophy of deterrence: Washington, in this view, would never allow U.S. troops to
be overrun, and would ultimately defend them with nuclear systems, if the need arose.
U.S. nuclear systems in Europe were a step on the ladder of flexible response.
Strategically, the United States and its allies sought to enhance the link between U.S. forces
in Europe and the U.S. strategic nuclear arsenal with the 1979 alliance decision to base U.S.
intermediate nuclear forces (INF) in Europe. The forward deployment in Germany (and
elsewhere) of these mobile and highly accurate missiles was meant to signal Moscow -- and
reassure the allies -- that these systems, controlled by the United States, could be employed
to defeat a Soviet invasion.
Doubts over the U.S. commitment to Article V endured throughout the Cold War.
The Strategic Defense Initiative (SDI), proposed in 1984, provoked criticism that the Reagan
Administration wished to create a system that could shield the United States, but not its
allies, against nuclear attack. In the language of the era, Europeans viewed SDI as
"decoupling" the link between the United States and western Europe. Reagan Administration
officials countered that SDI, by protecting the United States from nuclear attack, made easier
any necessary decision in a conflict to use nuclear systems against the Soviets.
Article V After the Cold War
The collapse of the U.S.S.R. and the current disarray of the Russian military have
eliminated any significant threat to western Europe and the United States. NATO has
developed "new missions" relating to crisis management. Virtually all U.S. nuclear systems
have been removed from Europe; only a few hundred nuclear gravity bombs, of limited
military utility, remain. Official NATO doctrine does not describe Russia as an enemy,
nuclear systems are no longer targeted on Russia, and nuclear weapons are now for use
Lawrence Freedman, "NATO Myths," in George Thibault (ed.), The Art and Practice of Military5
Strategy. Washington, NDU Press, 1984. p. 692.
only in a "last resort" -- a different formulation from flexible response, where such weapons
were strategically mixed with conventional forces and might be used where appropriate
to defeat a Soviet attack.6
The Soviet threat bound the allies together. The risks that have replaced that threat
have given rise, in the view of some observers, to a "regionalization" in NATO that could
undermine the viability of Article V. Countries in one region of the alliance are concerned
about dangers inherent in their geographic neighborhoods that may not directly affect allies
in a distant corner of Europe. In 1991, there was a concrete example of regionalization.
When Turkey agreed to lend its bases as a staging area for airstrikes against Iraq in the
Persian Gulf War, Turkish officials indicated that they might invoke Article V if Iraq
retaliated. Initially, the German government was sharply critical of U.S. efforts to expel
Iraqi forces from Kuwait. Otto von Lambsdorff, then a key figure in the German coalition
government, said in response to the Turkish inquiry, "We are convinced that a missile attack
on Turkish territory does not require a NATO response." Some members of the German
Bundestag contended that it was Turkey, by allowing U.S. aircraft to attack targets from
Turkish bases, that had acted provocatively, and that Germany must not honor any request
from Ankara for assistance.7
NATO Expansion and Article V
The Administration continues to describe collective defense as the core of the alliance.
Before the Senate Armed Services Committee on April 23, 1997, Sen. Kempthorne asked:
"...if NATO is not anti-Russian, then what is it? Who is the alliance defending against?"
Secretary of State Albright responded:
The threat is basically...the instability within the region and which has in fact created
two world wars. But there is also the possibility of an outside threat. There is a
possibility of threats from various parts outside the region, to the south, we have to
guard against. And, on the off chance that in fact Russia does not turn out the way
we are hoping it will and its current leadership wants, NATO is there.8
Some observers believe that the importance of Article V, in the absence of a Russian
threat, is at least temporarily diminished. They express concern that the growing importance
for NATO of non-Article V missions is making the alliance more a collective security than
a collective defense organization. "Regionalization," in this view, could dilute the
effectiveness of the alliance. NATO's mission in Bosnia has not been undertaken to respond
to or prevent an attack on an ally, but rather as "crisis management." Reaching unanimity
for the long term in bringing stability to Bosnia is proving difficult. Some allies see an element
of "regionalization" in enlargement of the alliance. Officials from Italy, Greece, and Turkey,
See Library of Congress. CRS. NATO Nuclear Strategy: Issues for U.S. Policy, by Stanley R.6
Sloan. CRS Report 96-653. July 25, 1996.
"Germany reluctant to defend Turkey if Iraq retaliates," Washington Post, Jan. 22, 1991. p. A20.7
Ultimately, Chancellor Kohl sent aircraft to Turkey to be used to defend Turkish airspace, but not
for attack against Iraq.
"Hearing on NATO Enlargement," Senate Armed Services Committee. April 23, 1997. unpaginated8
for example, have stronger concerns about stability in the Balkans than do the Norwegians
or the Danes. In the debate over enlargement, Rome, Athens, and Ankara supported the
entry into NATO of Slovenia and Romania as a means to assure stability; the Nordics
opposed the candidacies of these two countries, and the Danes urged the admission of the9
NATO remains an organization geared for collective defense, and leaders of NATO
states point out that the Organization for Security and Cooperation in Europe (OSCE) serves
the purpose of collective security through such actions as monitoring human rights,
arbitrating conflicts, and overseeing elections in selective member states. NATO, in contrast,
insists that candidates for membership resolve ethnic and border conflicts before entering
the alliance. An exception to this rule has been NATO's effort to manage tensions between
Greece and Turkey, both alliance members.
Agreeing upon a cohesive response to threats short of war is difficult, due to geography,
political traditions, and economic need. Article V raises the possibility of a range of
responses to counter a threat: An ally may take "such action as it deems necessary, including
the use of armed force, to restore and maintain the security of the North Atlantic area."
Presumably, such action could be an economic embargo or other steps, short of force, to
compel a state threatening an ally to adopt a more benign policy. Some Administration
officials are discussing nuclear proliferation with candidate states as a threat that could cause
Article V to be invoked. It is not clear that all allies would agree that Article V is appropriate
for such a threat. At the same time, the important difference from the era of "collective
security" between the World Wars is that the United States is clearly engaged in Europe
as NATO's leader, and maintains the capacity to deter or defeat an adversary that threatens
an ally's survival.
See Library of Congress. CRS. NATO Enlargement: Process and Allied Views, by Paul E. Gallis.9
CRS Report 97-666. p. 14-20.