International Security and Military Alliances

A central pillar of the world order the US established in the period after World War II was the principle of collective security which says that nations will contribute to collective military operations and/or using economic sanctions in response to international aggression. This principle was also the basis for the US establishing military alliances and mutual defense treaties with other countries or groups of countries. This principle has become more controversial recently as some have questioned whether the US should sustain such commitments.

As NATO celebrated its 70th anniversary, there was a debate about whether NATO is obsolete. Also, the fact that NATO members are not meeting the agreed-upon requirement of spending 2% of GDP for defense has prompted calls for the US to threaten to pull out of NATO if members do not increase their defense spending.

Also subject to debate are US treaties with Asian countries. Since 1953 the US has had a mutual defense treaty with South Korea and has 24,000 US troops based in South Korea in support of its commitment. Since 1960, the US has had a treaty with Japan that says that the two countries pledge to join forces and act together if there is an armed attack against Japan or against the 39,000 US forces based there.

Proposals with bipartisan support discussed below:

  • Making it a high priority in US foreign policy to uphold the principle of collective security
  • Continuing to be a member of NATO
  • Threatening to withdraw from NATO if European members do not increase defense spending
  • Continuing to have a mutual defense treaty with South Korea
  • Continuing to have 24,000 US troops in South Korea
  • Continuing to have a mutual security treaty with Japan
  • Continuing to have 39,000 US troops in Japan

There were no proposals that failed to receive bipartisan support.

UPHOLDING THE PRINCIPLE OF COLLECTIVE SECURITY

All nations face the risk of being attacked or invaded by another nation.  The key trigger for World War II was that Germany and Japan invaded neighboring countries.  

After the war, the major countries in the world agreed in the United Nations Charter that the use of military force against another country is a violation of international law, unless it is in self-defense, collective defense, or is approved by the UN Security Council.  

But, because there is no international police force to enforce the law, they also agreed that when a country comes under attack, other countries should join together to defend the country being attacked, not only through military force, but also through economic sanctions.  This is the principle of “collective security.” 

The idea is that leaders who might have the desire to conquer neighboring countries, will be deterred or dissuaded if they believe that other countries will join together to come to the defense of the country.  Some countries have collective defense agreements in which they promise to come to each other’s aid if attacked. We’ll look at those types of alliance arrangements shortly. 

They were then informed about the UN Charter and the role of the UN Security Council and evaluated two pairs of arguments for and against making collective security a high priority in US foreign policy.

The arguments in favor did substantially better, overall and among both parties.. The pro arguments were found convincing by large bipartisan majorities of over eight in ten. The con arguments did quite poorly, especially among Democrats, but were found convincing by a majority of Republicans. Overall, less than half found the con arguments convincing.

Finally, they were asked whether it should, “be a high priority in U.S. foreign policy to uphold the principle of collective security, by contributing to collective military operations and/or using economic sanctions in response to international aggression?” A large bipartisan majority of over eight in ten said it should, including 77% of Republicans and 89% of Democrats.

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A bipartisan majority has favored the use of US troops if an ally is attacked:

  • Asked whether they would favor the “use of US troops” if a “US ally is invaded,” 85% were in favor, including 91% of Republicans and 85% of Democrats. (2018, Chicago Council on Global Affairs)
  • Asked whether they would favor the “use of US troops,” if “another country seizes territory belonging to a US ally,” 73% were in favor, including 77% of Republicans and 74% of Democrats. (2018, Chicago Council on Global Affairs)

Very large bipartisan majorities have stated for several decades that defending our allies should be an important US foreign policy goal:

  • Between 1974 and 2015, asked whether “defending our allies’ security,” should be a very, somewhat or not an important US foreign policy goal, 83 - 94% have said it should be very (33 - 57%) or somewhat (35 - 55%) important. In 2015, 93% (Republicans 93%, Democrats 95%) said it should be very (38%, Republicans 43%, Democrats 38%) or somewhat (55%, Republicans 49%, Democrats 57%) important. (2015, Chicago Council on Global Affairs)

MUTUAL DEFENSE TREATIES

Respondents were first provided a briefing on the NATO mutual defense treaty which covered its history and membership. Most centrally, they were told:

The NATO charter includes a key section, called Article 5, which says that NATO members regard an attack on any member as an attack on all and that all members will defend any member that is attacked.

They were also told:

While a key focus is the potential for an attack by Russia, NATO has addressed other issues as well. Right now, there are several NATO countries participating in the operation in Afghanistan, in addition to the U.S.

They received a description of the working relationship between the NATO militaries and told:

The U.S. keeps about 65,000 troops stationed in Europe to help defend Europe if necessary and to send a signal of its commitment to help defend Europe. The European members have 1.7 million troops stationed in Europe.

Finally they were told, “Currently, there is some debate about whether the U.S. should continue to be part of NATO.”

They then evaluated two pairs of arguments in favor of and against continuing to be part of NATO. The arguments in favor did substantially better than those against, overall and among partisans. Only one argument against was found convincing by a majority of Republicans -- a bare majority -- while neither was found convincing by a majority of Democrats.

Finally, asked whether “they think the U.S. should or should not continue to be part of the NATO military alliance?” an overwhelming 83% said they think the US should continue to be part of NATO. This included 90% of Democrats, and 77% of Republicans.

Millennials (age 18‐34), who could conceivably be less attuned to the concern about the threat from Russia due to coming of age after the end of the Cold War, were nonetheless overwhelmingly supportive of NATO membership at 77%.

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With no background information, majorities have favored the US maintaining its commitment to NATO:

  • Told that NATO is “the military alliance among western nations” and asked whether they “think the NATO alliance should be maintained, or is this alliance not necessary anymore,” 77% favored maintaining it, including 70% of Republicans and 88% of Democrats. (March 2019, Gallup)
  • Asked whether the US “should increase our commitment to NATO, keep our commitment what it is now, decrease our commitment to NATO, or withdraw from NATO entirely,” 75% (Republicans 65%, Democrats 87%) favored keeping the commitment the same (57%, Republicans 59%, Democrats 57%) or increasing the commitment (18%, Republicans 6%, Democrats 30%), while 16% wanted to decrease it (Republicans 28%, Democrats 7%), and 4-6% wanted to withdraw entirely. (2018, Chicago Council on Global Affairs) 
  • A large majority said that NATO is “still essential to our country’s security,” 69% (Republicans 58%, Democrats 83%). (2017, Chicago Council on Global Affairs) 

A bipartisan majority has supported the general principle that the US should use military force to defend allies:

  • Asked whether they would favor the “use of US troops” if a “US ally is invaded,” 85% were in favor, including 91% of Republicans and 85% of Democrats. (2018, Chicago Council on Global Affairs)
  • Asked whether they would favor the “use of US troops,” if “another country seizes territory belonging to a US ally,” 73% were in favor, including 77% of Republicans and 74% of Democrats. (2018, Chicago Council on Global Affairs)

When the military commitments of NATO membership have been specified, a bipartisan majority has favored the US making such a commitment, but the majority is smaller, and a large share has not provided an answer.  But few oppose the commitment. 

  • Respondents were informed that, “As a member of the NATO alliance, an attack on one of the NATO members is considered to be an attack on the US and the US is obligated to come to the defense of the NATO member that has been attacked.” Then, asked whether, “ the US should maintain its commitment to defend NATO allies when attacked or is this no longer necessary,” 57% favored the US maintaining its commitment (Democrats 71%, Republicans 53%). An exceptionally large 32% did not provide an answer (Democrats 25%, Republicans 28%). Just 11% said the commitment is no longer necessary (Democrats 4%, Republicans 19%). (March 2019, YouGov)

With no background information, and offered a non-committal option, support for maintaining US membership in NATO has dropped to a plurality, with a large share taking a non-committal position:

  • Asked whether they support “the US’ membership of NATO,” a plurality were in support (44%, Republicans 41%, Democrats 60%, ) and a small number opposed (10%,  Republicans 18%, Democrats 3%).  A substantial number chose “neither support nor oppose”(Republicans 20%, Democrats 14%) , and an even larger number (29%) did not provide an answer. (March 2019, YouGov)

Respondents were presented the following briefing material as part of an in-person deliberative poll by Stanford University’s Center for Deliberative Democracy in September 2019:

During and after the Cold War, the US led its partners through alliances and free trade agreements that focused on strategic areas of the globe. The North Atlantic Treaty Organization (NATO), an alliance of the US, Canada, and over twenty European countries, requires members to defend any member attacked by an outside power. Originally, it was part of the US strategy for protecting Western Europe from invasion by the Soviet Union.

After the Cold War, NATO expanded to several former Soviet satellites bordering Russia thus antagonizing that country. At the same time, many Western European members significantly reduced their defense spending. In 2014, NATO members all committed to spend 2% of their gross domestic product on defense by 2024, a goal first set in 2002. 

They were then presented a proposal, and arguments for and against it:

Proposal: The US should reaffirm its commitment to defend any NATO ally attacked by a hostile force.

Argument in Favor: President Trump has repeatedly called this commitment in question, demoralizing our allies and increasing the chances of Russian military intervention. Our European allies have never in fact called upon the US to repel attacks. Only the US has used NATO this way, in response to 9/11. NATO members honored our call for war against Afghanistan.

Argument Against: The NATO commitment increases the chances of war with Russia. President Trump should require large increases in European defense spending before reaffirming our commitment.

After reading the briefing material, respondents deliberated with each other in-person before making their final recommendation. On a 0-10 scale, with 5 being “in the middle”, a large bipartisan majority of 83% favored the US reaffirming its commitment to NATO (6-10), including 77% of Republicans and 90% of Democrats.

Pre-Deliberation Poll
Before receiving any briefing materials or engaging in the deliberation process respondents were given the same poll question as those asked afterwards. Support increased from the pre-deliberation poll to the post-deliberation poll, overall (72% to 83%), and among Republicans (59% to 77%) and Democrats (81% to 90%). 

Respondents were introduced to the dispute between the US and European NATO members over defense spending levels:

For some years now there has been a dispute between the U.S. and other members of NATO about their level of defense spending. The U.S. has complained that it spends about 4-5% of the U.S. economy on its military, while European nations generally spend about 2% or less, some as low as 1%. Europeans point out that the amount that the U.S. spends is not only in Europe but also in Asia and in the U.S. homeland, and that Europe already spends twice as much as Russia, which is NATO’s primary focus.

Nonetheless, in 2014, the European NATO partners agreed to set a goal to increase their defense spending to at least 2% of their budget. There have been some increases, but only 4 of the 26 European countries have met this goal, though several more are expected to reach this level within the year. One of the largest countries, Germany, is unlikely to reach it at any point in the near future.

They were then told that there is some debate about what the U.S. should do about this situation and were asked to evaluate three options with an argument in favor of each one. Three possible approaches were presented.

They were presented the first proposal and an argument in favor:

Press European countries to spend more on their military and say that if they do not the U.S. will disengage from Europe militarily and possibly withdraw from NATO

The argument did only moderately well with an overall majority of 56% finding it convincing.

However, there was a sharp partisan divide: 76% of Republicans, but only 39% of Democrats found it convincing. 

They were presented the second proposal and an argument in favor:

Press European countries to spend more on their military, but NOT threaten to disengage from Europe or withdraw from NATO.

The argument did far better than the first argument. Overall 80% found it convincing as did 87% of Democrats. Among Republicans, 72% found it convincing— roughly the same as the 76% who found the argument for the first proposal convincing— suggesting substantial ambivalence. 

They were presented the third proposal and an argument in favor:

Remain part of NATO but reduce U.S. military investments in Europe to bring them more in line with the level that the Europeans make. 

The argument also did quite well with 74% finding it convincing. Among Republicans (77%) it did the best of all arguments, with 72% of Democrats concurring.

Asked for their final recommendation, the least attractive option was to threaten withdrawal from Europe and NATO, which was endorsed by just 12% overall—one in five Republicans and a miniscule 4% of Democrats.  The clear favorite, endorsed by about half overall and by both parties, was the third option: remaining part of NATO but reducing US military spending in line with European defense spending. The option of pressing the Europeans but not threatening withdrawal was endorsed by 35% overall— Republicans 29%, Democrats 41%.

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As a way to increase NATO members’ defense spending, and offered two options, a majority has favored the US using diplomacy rather than threatening to withdraw, though Republicans diverge.  

  • Respondents were told that, “As you may know, the United States has long urged its NATO allies to spend more on defense. They have recently agreed to increase defense spending but have not yet done so.” They were then asked to choose between two options.  The option that was the most popular overall and with Democrats was:
  • “The United States should encourage greater allied defense spending through persuasion and diplomatic means while maintaining a firm commitment to defend NATO members,” (58%,  Democrats 72%, Republicans 45%). 
  • However a slight majority of Republicans favored the second option: “The United States should withhold its commitment to defend NATO members until NATO allies actually spend more on defense,” (38%, Republicans 52%, Democrats 25%). (2017, Chicago Council on Global Affairs)


As you may know, the United States has had a mutual defense treaty with South Korea since 1953. The U.S. keeps 24,000 troops in South Korea. These troops are to help defend South Korea if necessary and to send a signal of America’s commitment to help defend them.  The U.S. regularly does military exercises with South Korean forces to ensure that they will be able to work together effectively if it is necessary to defend them.  These troops are also used for other purposes in Asia. South Korea covers 40 percent of the costs of basing U.S. troops there. Currently, there is some debate about whether the U.S. should continue to have a mutual defense treaty with South Korea.

Finally, asked for their final recommendation, 87% favored keeping the treaty, with no partisan differences.

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Bipartisan majorities have favored using US troops to defend South Korea:

  • Asked whether the US should, “use military troops to help defend South Korea,” if they “were attacked by North Korea,” 68% said they should, including 74% of Republicans and 62% of Democrats. (April 2017, CNN/ORC)
  • Told that, “There has been some discussion about the circumstances that might justify using US troops in other parts of the world,” and asked whether they favor “the use of US troops...if North Korea invaded South Korea,” 62% were in favor, including 70% of Republicans and 59% of Democrats. (2017, Chicago Council on Global Affairs)

The argument in favor did overwhelmingly better. The pro argument was found convincing by nine in ten, overall and among both parties. The con argument was found convincing by just four in ten, overall and among both parties.

Asked for their final recommendation, three in four supported the US continuing to have 24,000 troops based in South Korea, including eight in ten Republicans and three in four Democrats.

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Majorities have favored the US having military bases in South Korea:

  • Asked whether the US should have “long-term military bases” in South Korea, 74% felt it should, including 81% of Republicans and 73% of Democrats. (2018, Chicago Council on Global Affairs)

Asked about the number of US troops in South Korea, clear majorities have found the number acceptable. 

  • Told that the “United States currently has about 30,000 troops in South Korea,” 34% thought it was “too many” (Republicans 27%, Democrats 39%), while 62% (Republicans 69%, Democrats 59%) said it was about right (50%) or too few (12%) (June 2010, Global Views)

Majorities would favor partial withdrawal of US troops from South Korea if North Korea agreed to give up its nuclear arsenal, but not complete withdrawal:

  • Asked whether they support “partial withdrawal of US forces from South Korea,” if “the United States and North Korea reach an agreement in which North Korea gives up its nuclear weapons,” 52 - 54% were in support, with 41 - 44% opposed. (June 2010, Chicago Council on Global Affairs)
  • Asked whether they favor or oppose, “complete withdrawal of US forces from South Korea,” if “the United States and North Korea reach an agreement in which North Korea gives up its nuclear weapons,” 77 - 82% were opposed, and 14 - 18% favored. (2018, Chicago Council on Global Affairs)

Respondents were briefly informed about the mutual security treaty, and US military presence in Japan:

As you may know, the United States has had a mutual security treaty with Japan since 1960.  According to this treaty, the two countries pledge to join forces and act together if there is an armed attack against Japan or against U.S. forces based there.

The U.S. keeps 39,000 troops stationed in Japan. These troops are to help defend Japan, if necessary, and to send a signal of America’s commitment to them.  The U.S. regularly does military exercises with Japanese forces to ensure that they will be able to work together effectively if it is necessary to defend them. These troops are also used for other purposes in Asia. 

Japan covers 75 percent of the cost of basing U.S. troops there. Currently, there is some debate about whether the U.S. should continue to have this mutual security treaty with Japan. 

Finally, asked for their final recommendation, 87% favored keeping the treaty, with no significant partisan differences (Republicns 88%, Democrats 87%).

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A bipartisan majority has favored using US troops to defend Japan against North Korea, but majority support is quite recent:

  • Asked whether they favor, “the use of U.S. troops” if “North Korea attacks Japan,” 64% were in favor, including 71% of Republicans and 62% of Democrats. (2018, Chicago Council on Global Affairs)

A majority has opposed the use of US troops to defend Japan if they enter a conflict with China over disputed islands, with opposition decreasing since 2015:

  • Asked whether they support the “use of U.S. troops” if “China initiates a military conflict with Japan over disputed islands,” 55% opposed, including 50% of Republicans and 57% of Democrats. (2018, Chicago Council on Global Affairs)

The argument in favor did overwhelmingly better. The pro argument was found convincing by around 87%, including 88% of Republicans and 85% of Democrats. The con argument was found convincing by just four in ten, overall and among both parties.

Asked for their final recommendation, three in four supported the US continuing to have 39,000 troops based in Japan, including eight in ten Republicans and three in four Democrats.

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A bipartisan majority has favored the US having military bases in Japan, but this has been decreasing since 2014:

  • Asked whether the US should have, “long-term military bases” in Japan, 65% felt they should, including 73% of Republicans and 64% of Democrats. (2018, Chicago Council on Global Affairs)

Asked about the number of 39,000 US troops in Japan, a majority has found the number acceptable. 

  • Told that the “United States currently has about 33,000 troops in Japan, including Okinawa” 44% thought it was too many (Republicans 38%, Democrats 50%), while 52% (Republicans 60%, Democrats 44%) thought it was about right (47%) or too few (5%). (June 2010, Chicago Council on Global Affairs)