List of national four-country border sets
==Geometry and geography==
[[Image:Enclave-of-Three.png|left|thumb|Englave of Three|figure 1]]
[[Image:triclave.png|right|thumb|Triclave|figure 2]]
In [[Dimension|geometric 2-space]], no more than four continuous two-dimensional [[shape|shapes]] can all share one-dimensional [[Boundary|BOUNDARIES]] with each other. There are two ways this is possible, with three mutually-bordering shapes combining to form an [[enclave]] within the fourth (figure 1), or a single shape forming an enclave within the combination of three mutually-bordering shapes (figure 2). However, not all nations can be represented by single continuous two-dimensional shapes, and so the number of nations which can possibly share a border with each other is not necessarily limited to four.
{{clear}}
== Current national four-country border sets==
In typical cases, a four-country border set is formed when three mutually-bordering nations form a ring around a landlocked fourth (which borders only the other three), creating a "triclave" (see figure 2). [[Paraguay]], [[Luxembourg]], [[Burundi]], and [[Malawi]] are examples of nations that form the center of such configurations. However, [[exclave|exclaves]] and remote national territories create other possibilities. As of the 2006 breakup of [[Serbia and Montenegro|the State Union of Serbia and Montenegro]], there are nine four-nation sets in the world in which each nation shares a boundary (land or fresh water) with each other.
[[Image:PAR-BOL-BRA-ARG.png|right|thumb|Map of Paraguay|'''Paraguay''' (red), surrounded by the mutually-bordering '''Brazil''' (blue), '''Argentina''' (green), and '''Bolivia''' (magenta)]]
===In South America===
[[Paraguay]]-[[Brazil]]-[[Argentina]]-[[Bolivia]]
{| class="wikitable" style="text-align:center"; border="50"
! Borders(km) !! {{flagicon|Paraguay}} PAR !! {{flagicon|Brazil}} BRA !! {{flagicon|Argentina}} ARG !! {{flagicon|Bolivia}} BOL
|-
| {{flagicon|Paraguay}} '''PAR''' ||align="center"| - || 1290 || 1880 || 750
|-
| {{flagicon|Brazil}} '''BRA''' || 1290 ||align="center"| - || 1224 || 3400
|-
| {{flagicon|Argentina}} '''ARG''' || 1880 || 1224 ||align="center"| - || 832
|-
| {{flagicon|Bolivia}} '''BOL''' || 750 || 3400 || 832 ||align="center"| -
|}
[[Image:LUX-FRA-GER-BEL.png|right|thumb|Map of Luxembourg|'''Luxembourg''' (red), surrounded by the mutually-bordering '''France''' (blue), '''Germany''' (green), and '''Belgium''' (magenta)]]
===In Europe===
[[Luxembourg]]-[[France]]-[[Germany]]-[[Belgium]]
{| class="wikitable" style="text-align:center"; border="50"
! Borders(km) !! {{flagicon|Luxembourg}} LUX !! {{flagicon|France}} FRA!! {{flagicon|Germany}} GER!! {{flagicon|Belgium}} BEL
|-
| {{flagicon|Luxembourg}} '''LUX''' ||align="center"| - || 73 || 138 || 148
|-
| {{flagicon|France}} '''FRA''' || 73 ||align="center"| - || 451 || 620
|-
| {{flagicon|Germany}} '''GER''' || 138 || 203 ||align="center"| - || 167
|-
| {{flagicon|Belgium}} '''BEL''' || 148 || 241 || 167 ||align="center"| -
|}
[[Image:BIH-SRB-MNE-CRO.png|right|thumb|Map of Bosnia and Herzegovina|'''Bosnia and Herzegovina''' (red), surrounded by the mutually-bordering '''Serbia''' (blue), '''Montenegro''' (green), and '''Croatia''' (magenta)]]
[[Bosnia and Herzegovina]]-[[Serbia]]-[[Montenegro]]-[[Croatia]]<ref>[[Bosnia and Herzegovina]] has 20 km of coastline on the Adriatic Sea while Croatia borders Montenegro only through the non-contiguous southern portion of the Dubrovačko-neretvanska county (technically an exclave, though connected to the rest of Croatia by territorial waters)</ref>
{| class="wikitable" style="text-align:center"; border="50"
! Borders(km) !! {{flagicon|Bosnia and Herzegovina}} BIH !! {{flagicon|Serbia}} SRB !! {{flagicon|Montenegro}} MNE !! {{flagicon|Croatia}} CRO
|-
| {{flagicon|Bosnia and Herzegovina}} '''BIH''' ||align="center"| - || 302 || 225 || 932
|-
| {{flagicon|Serbia}} '''SRB''' || 302 ||align="center"| - || 203 || 241
|-
| {{flagicon|Montenegro}} '''MNE''' || 225 || 203 ||align="center"| - || 25
|-
| {{flagicon|Croatia}} '''CRO''' || 932 || 241 || 25 ||align="center"| -
|}
[[Image:BEL-GER-FRA-NED.png|right|thumb|Map of Belgium|'''Germany''' (green) and '''Belgium''' (red) each border both '''France''' (blue) and the '''Netherlands''' (magenta); the island of Saint Martin (Sint Maarten) contains a border between the '''Netherlands Antilles''' and the French '''Collectivité de Saint-Martin''']]
[[Belgium]]-[[Germany]]-[[Netherlands]]-[[France]]<ref> The only land boundary between the Netherlands and France is on the Caribbean island of [[Saint Martin]] (Sint Maarten), where the [[Netherlands Antilles]] meets the [[Saint_Martin_%28France%29|French Overseas Collectivity of Saint Martin]] </ref>
{| class="wikitable" style="text-align:center"; border="50"
! Borders(km) !! {{flagicon|Belgium}} BEL !! {{flagicon|Germany}} GER !! {{flagicon|Netherlands}} NED !! {{flagicon|France}} FRA
|-
| {{flagicon|Belgium}} '''BEL''' ||align="center"| - || 167 || 450 || 620
|-
| {{flagicon|Germany}} '''GER''' || 167 ||align="center"| - || 577 || 451
|-
| {{flagicon|Netherlands}} '''NED''' || 450 || 577 ||align="center"| - || 10
|-
| {{flagicon|France}} '''FRA''' || 620 || 451 || 10 ||align="center"| -
|}
[[Image:BLR-LTU-POL-RUS.png|right|thumb|Map of Belarus|'''Belarus''' (magenta), '''Lithuania''' (blue), and '''Poland''' (green) all border one another. The mainland of '''Russia''' (red) borders Belarus while her Baltic '''Kaliningrad Oblast''' borders both Lithuania and Poland]]
[[Belarus]]-[[Lithuania]]-[[Poland]]-[[Russia]]<ref>The Russian [[Kaliningrad Oblast]], an exclave on the [[Baltic Sea]] creates [[Russia|Russian]] borders with bother [[Lithuania]] and [[Poland]]. [[Belarus]] does not border Kaliningrad, but does share boundaries with mainland Russia, Lithuania, and Poland.</ref>
{| class="wikitable" style="text-align:center"; border="50"
! Borders(km) !! {{flagicon|Belarus}} BLR !! {{flagicon|Lithuania}} LTU !! {{flagicon|Poland}} POL !! {{flagicon|Russia}} RUS
|-
| {{flagicon|Belarus}} '''BLR''' ||align="center"| - || 502 || 407 || 959
|-
| {{flagicon|Lithuania}} '''LTU''' || 502 ||align="center"| - || 91 || 227
|-
| {{flagicon|Poland}} '''POL''' || 407 || 91 ||align="center"| - || 206
|-
| {{flagicon|Russia}} '''RUS''' || 959 || 227 || 206 ||align="center"| -
|}
[[Image:AZE-ARM-TUR-IRN.png|right|thumb|Map of Nakhichevan Region of Azerbaijan|'''Azerbaijan''' (red), whose '''Nakhichevan Region''' is surrounded by the mutually-bordering '''Armenia''' (green), '''Turkey''' (magenta), and '''Iran''' (blue)]]
===In Asia<ref>The 40km border between China's [[Xinjiang]] Autonomous Region and Russia's [[Altai Republic]] is all that prevents [[Mongolia]], [[Kazhakstan]], [[Russia]], and the [[People's Republic of China]] from forming a four-nation border set.</ref>===
[[Nakhichevan|Nakhichevan(Azerbaijani exclave)]]-[[Armenia]]-[[Turkey]]-[[Iran]]
{| class="wikitable" style="text-align:center"; border="50"
! Borders(km) !! {{flagicon|Azerbaijan}} AZE !! {{flagicon|Armenia}} ARM !! {{flagicon|Turkey}} TUR !! {{flagicon|Iran}} IRN
|-
|{{flagicon|Azerbaijan}} '''AZE''' ||align="center"| - || 221<ref name="Nakhichevan">Numbers refer to the [[Nakhichevan]] exclave of Azerbaijan; the total lengths of the [[Azerbaijan|Azerbaijani]]-[[Armenia|Armenian]] and [[Azerbaijan|Azerbaijani]]-[[Iran|Iranian]] borders are 787km and 611km, respectively. [[Turkey]] does not border the main portion of Azerbaijan.</ref> || 9 || 179<ref name="Nakhichevan"/>
|-
|{{flagicon|Armenia}} '''ARM''' || 221<ref name="Nakhichevan"/> ||align="center"| - || 268 || 35
|-
|{{flagicon|Turkey}} '''TUR''' || 9 || 268 ||align="center"| - || 499
|-
|{{flagicon|Iran}} '''IRN''' || 179<ref name="Nakhichevan"/> || 35 || 499 ||align="center"| -
|}
[[Image:BDI-RWA-TAN-COD.png|right|thumb|Map of Burundi|'''Burundi''' (green), surrounded by the mutually-bordering '''Rwanda''' (red), '''Tanzania''' (blue), and '''Congo-Kinsasha''' (magenta)]]
===In Africa<ref>The 2km border between Zambia and Botswana at Africa's "four corners" is all that prevents the group [[Botswana]]-[[Namibia]]-[[Zimbabwe]]-[[South Africa]] from satisfying the criteria of four mutually-bordering nations (click [[Quadripoint#International%20quadripoints|here]] for more information)</ref>===
[[Burundi]]-[[Rwanda]]-[[Tanzania]]-[[Democratic_Republic_of_the_Congo|Congo(Kinshasa)]]<ref name="Tanganyika">The border between Congo-Kinsasha and Tanzania is entirely aquatic; the two nations are separated by [[Lake Tanganyika]]</ref>
{| class="wikitable" style="text-align:center"; border="50"
! Borders(km) !! {{flagicon|Burundi}} BDI !! {{flagicon|Rwanda}} RWA !! {{flagicon|Tanzania}} TAN !!{{flagicon|Democratic_Republic_of_the_Congo}} COD
|-
| {{flagicon|Burundi}} '''BDI''' ||align="center"| - || 209 || 451 || 233
|-
| {{flagicon|Rwanda}} '''RWA''' || 209 ||align="center"| - || 217 || 217
|-
| {{flagicon|Tanzania}} '''TAN''' || 451 || 217 ||align="center"| - || 459
|-
| {{flagicon|Democratic_Republic_of_the_Congo}} '''COD''' || 233 || 217 || 459 ||align="center"| -
|}
[[Image:RWA-UGA-COD-TAN.png|right|thumb|Map of Rwanda|'''Rwanda''' (red), bordered by the mutually-bordering '''Uganda''' (green), '''Congo(Kinsasha)''' (magenta), and '''Tanzania''' (blue)]]
[[Rwanda]]-[[Uganda]]-[[Democratic_Republic_of_the_Congo|Congo(Kinshasa)]]-[[Tanzania]]<ref name="Tanganyika"/>
{| class="wikitable" style="text-align:center"; border="50"
! Borders(km) !! {{flagicon|Rwanda}} RWA!! {{flagicon|Uganda}} UGA !! {{flagicon|Democratic_Republic_of_the_Congo}} COD !! {{flagicon|Tanzania}} TAN
|-
| {{flagicon|Rwanda}} '''RWA''' ||align="center"| - || 169 || 217 || 217
|-
| {{flagicon|Uganda}} '''UGA''' || 169 ||align="center"| - || 765 || 396
|-
| {{flagicon|Democratic_Republic_of_the_Congo}} '''COD''' || 217 || 765 ||align="center"| - || 459
|-
| {{flagicon|Tanzania}} '''TAN''' || 217 || 396 || 459 ||align="center"| -
|}
[[Image:MWI-MOZ-ZAM-TAN.png|right|thumb|Map of Malawi|'''Malawi''' (red), surrounded by the mutually-bordering '''Mozambique''' (magenta), '''Zambia''' (green), and '''Tanzania''' (blue)]]
[[Malawi]]-[[Mozambique]]-[[Zambia]]-[[Tanzania]]
{| class="wikitable" style="text-align:center"; border="50"
! Borders(km) !! {{flagicon|Malawi}} MWI!! {{flagicon|Mozambique}} MOZ !! {{flagicon|Zambia}} ZAM !! {{flagicon|Tanzania}} TAN
|-
| {{flagicon|Malawi}} '''MWI''' ||align="center"| - || 1569 || 837 || 475
|-
| {{flagicon|Mozambique}} '''MOZ''' || 1569 ||align="center"| - || 419 || 756
|-
| {{flagicon|Zambia}} '''ZAM''' || 837 || 419 ||align="center"| - || 338
|-
| {{flagicon|Tanzania}} '''TAN''' || 475 || 756 || 338 ||align="center"| -
|}
==Former border sets of at least four countries==
The first two sets below include boundaries shared by former colonial empires (specifically territorial claims in [[South_america#European_colonization|South America]], [[Colonial Africa|Africa]], [[Colonial India|India]], [[History of Europe|Europe]], and the [[East India Company|East]] and [[West India Company|West]] Indies), and thus do not reflect geographic enclaves or triclaves.
{| class="wikitable" style="text-align:center"; border="50"
! Countries !! From !! To !! Terminal Event
|-
| [[Image:Pavillon royal de France.svg|border|22px]] [[French Empire|FRA]]<ref>Between 1704 and 1713, [[French Empire|France]] and her colonies neighbored the Netherlands (on [[Saint Martin]]), Spain (in Europe), Portugal (between [[French Guyana]] and Portugese [[Brazil]]) and Great Britain (between the [[Colonial India|Indian]] settlements of [[Hugli-Chuchura#History|Hughli]] and [[Chandernagar]]).</ref>, [[Image:Prinsenvlag.svg|border|22px]] [[Dutch Empire|NED]]<ref>Between 1704 and 1713, the [[Dutch Empire|Netherlands]] and her colonies neighbored France (on [[Saint Martin]]), Spain (in Europe between [[Dutch Republic]] and the [[Spanish Netherlands]]), Portugal (between Dutch [[Suriname]] and Portugese [[Brazil]]), and Great Britain (between the [[Colonial India|Indian]] settlements of [[Pulicat]] and [[Madras]].</ref>, [[Image:Bandera de España(1701-1748).gif|border|22px]] [[Spanish Empire|ESP]]<ref>Between 1704 and 1713, [[Spanish Empire|Spain]] and her colonies neighbored France (in Europe), the Netherlands (in Europe between [[Spanish Netherlands]] and the [[Dutch Republic]]), Portugal (in Europe and South America), and Great Britain (with the 1704 British capture of [[Gibraltar]]).</ref>, [[Image:Flag Portugal (1707).svg|border|22px]] [[Portugese Empire|POR]]<ref>Between 1704 and 1713, [[Portugese Empire|Portugal]] and her colonies neighbored France (between Portugese [[Brazil]] and [[French Guyana]]), the Netherlands (between Brazil and Dutch [[Suriname]]), Spain (in Europe and South America), and Great Britain (between the [[Colonial India|Indian]] settlements of [[Daman and Diu]] and [[Surat]]).</ref>, [[Image:Union flag 1606 (Kings Colors).svg|border|22px]] [[British Empire|GBR]]<ref>Between 1704 and 1713, the [[Kingdom of Great Britain]] (and prior to the 1707 [[Acts of Union 1707|Acts of Union]], the [[Kingdom of England]]) and her colonies neighbored France (between the [[Colonial India|Indian]] settlements of [[Chandernagar]] and [[Hugli-Chuchura#History|Hughli]]), the Netherlands (between the [[Colonial India|Indian]] settlements of [[Madras]] and [[Pulicat]]), Spain (with the 1704 British capture of [[Gibraltar]]), and Portugal (between the [[Colonial India|Indian]] settlements of [[Daman and Diu]] and [[Surat]])</ref> || 1704 || 1713 || Signing of the [[Treaty of Utrecht]] on 11APR1713
|-
| [[Image:Flag of Belgium (civil).svg|border|22px]] [[Belgian colonial empire|BEL]]<ref>European [[Belgium]] bordered France, the Netherlands, and Germany. The [[Belgian Congo]] bordered Portuguese Angola and several French and British colonies in Africa.</ref>, [[Image:Flag of Portugal.svg|border|22px]] [[Portugese Empire|POR]]<ref>European [[Portugal]] bordered Spain. In 1914, the African colonies of Mozambique, Angola, and Guinea-Bissau bordered territories held by Germany (Namibia and Tanganyika), Great Britain, France, and Belgium. The colony of [[East Timor|Timor Leste]] bordered the Dutch East Indies.</ref>, [[Image:Flag of the German Empire.svg|border|22px]] [[German Empire|GER]]<ref>Immediately prior to [[World War I]], European [[German Empire|Germany]] bordered the Netherlands, Belgium, and France. African colonies shared boundaries with territories held by Great Britain, Portugal, France, and Belgium</ref>, [[Image:Flag of France.svg|border|22px]] [[French Empire|FRA]]<ref>European [[France]] shared borders with Belgium and Germany. Vast French holdings in [[Scramble for Africa|colonial Africa]] abutted colonies possessed by Great Britain, Belgium, Germany, and Portugal. In South America, [[French Guyana]] bordered Dutch Suriname.</ref>, [[Image:Flag of the United Kingdom.svg|border|22px]] [[British Empire|GBR]]<ref>British colonies in Africa shared boundaries with territories held by France, Belgium, Germany, and Portugal. In South America, [[History of Guyana|British Guyana]] bordered Dutch Suriname.</ref>, [[Image:Flag of the Netherlands.svg|border|22px]] [[Dutch Empire|NED]]<ref>The European [[Netherlands]] shared borders with Germany and Belgium. The Dutch [[Dutch East India Company|East]]and [[Dutch West India Company|West]] India Companies controlled territories that bordered colonies of Portugal (on the island of Timor), Great Britain (Guyana), and France (French Guyana).</ref> || late 1800s || 1914 || Outbreak of [[World War I]]
|-
| [[Image:NF_1987_-_1992.jpg|border|22px]] [[Afghanistan|AFG]], {{flagicon|USSR}} [[Soviet Union|SUN]], {{flagicon|Pakistan}} [[Pakistan|PAK]]<ref>From 15AUG1947 to 16DEC1971, Pakistan included modern-day Bangladesh (known as [[East Pakistan]])</ref>, {{flagicon|Iran}} [[Iran|IRN]] || 1947 || 1991 || Breakup of the [[Soviet Union]]
|-
| {{flagicon|Kosovo}} [[Kosovo|UNK]]<ref>The United Nations has been administering the region of Kosovo (in southern Serbia) since 1999</ref>, {{flagicon|SCG}} [[Serbia and Montenegro|SCG]]<ref>From 27APR1992 to 4FEB2003, the union of Serbia and Montenegro was called the Federal Republic of Yugoslavia (FRY)</ref>, {{flagicon|Albania}} [[Albania|ALB]], {{flagicon|Macedonia}} [[Republic of Macedonia|MKD]] || 1999 || 2006 || Formal dissolution of the [[Serbia and Montenegro|State Union of Serbia and Montenegro]]
|}
==See also==
* [[List of land border lengths]]
* [[List of countries that border only one other country]]
* [[List of national border changes since World War I]]
* [[List of island nations]]
* [[List of divided islands]]
* [[Landlocked]]
* [[Enclave]]
* [[List of enclaves and exclaves]]
* [[Foreign Enclaves in China]]
* [[Island country]]
* [[Quadripoint]]
==Notes==
<div class="references-small" style="-moz-column-count:2; column-count:2;">
<references /></div>
== Sources ==
*CIA World Factbook [https://www.cia.gov/library/publications// CIA World Factbook] (public domain)
*International Organization for Standardization (ISO): [http://www.iso.org/iso/country_codes.htm ISO 3166 Maintenance Agency] (or [[Comparison_of_IOC%2C_FIFA%2C_and_ISO_3166_country_codes|compare codes]])
[[Category:Lists of countries|Borders, land]]
[[Category:Borders]]