What is a border? Why are there more and more of them?
A border (or frontier) is the line where one state's land, laws and rights end and another's begin. Borders are drawn between states, and they also cut through seas, air and rivers.
The world has more borders now than 100 years ago. When the United Nations began in 1945 it had 51 members; today it has 193. Why?
- End of empires (decolonisation): from 1945 to the 1970s, colonies in Asia and Africa became independent states.
- Break-up of big states: in 1991 the Soviet Union split into 15 states, and Yugoslavia broke into several.
- Wish for self-rule: groups that feel different want their own state.
More borders also means more checks. Since the 1990s many states have built fences and walls to control migration, smuggling or conflict, even though trade and the internet cross borders easily. A border can open for goods and close for people.
Remember W-W-C: Where is the line, Who drew it, Can we cross.
Natural and ruled lines
Natural borders follow rivers, mountain crests, lakes or coasts. They are easy to see and often useful for defence. But a river can change its course, and people live on both banks, so a river border is not always simple.
Ruled (geometric) borders are straight lines, often along a latitude or longitude, drawn on a map. They are quick to draw but ignore how people actually live. Many straight borders appear in deserts and in lands that outside powers divided.
No border is 'perfect'. What matters is whether the people on both sides accept it, and whether it can be explained and kept in treaties.
Borders to protect: the Roman limes on the Rhine
The Roman Empire needed to keep raiders out and to control trade. Along the Rhine and the Danube rivers, and in some places across land between them, it built a frontier called the limes (a Latin word for a path or boundary).
- Forts, watchtowers and signal posts placed a few hundred metres to a few kilometres apart.
- Roads for soldiers to move quickly.
- In places, ditches, palisades or walls.
- Trading posts: the frontier was also a place for markets and customs.
So the limes was not a sealed wall. It was a controlled zone that kept watch, taxed trade and let people cross at set points. This idea of a border as a protective and managed zone is the same one used today in buffer strips and border posts.
Borders drawn by outsiders: the Berlin Conference and Africa
In 1884 to 1885 representatives of European states and a few others met in Berlin. No African ruler was invited. They agreed rules for claiming land in Africa: a power had to show it really controlled ('effective occupation') a coast or region. This started a rush to claim territory, called the partition of Africa. By 1914 outside powers controlled about 90 per cent of the continent.
Many borders were drawn on paper in Europe, with straight lines along latitudes and longitudes or along rivers. They often cut through peoples with one language and culture and joined groups that had little in common.
When African countries became independent in the 1950s and 1960s, they mostly kept these borders. In 1964 the Organisation of African Unity agreed to respect colonial borders, because redrawing them could start many conflicts. Today, trade zones and the African Union try to make the borders easier to cross.
A closed border: the two Koreas
In 1945, after the Second World War, Korea was split at the 38th parallel (a line of latitude) into a northern and a southern zone. In 1950 war broke out. It ended in 1953 with an armistice (a ceasefire), not a peace treaty.
The new border is a strip about 250 km long and 4 km wide called the Demilitarised Zone (DMZ). Soldiers of both sides stay back from the centre line, but outside the strip each side keeps large forces, so it is among the most heavily guarded borders in the world.
Because people have almost no contact, the strip has become a place where wildlife has recovered. This shows that a border is not only about people but also changes nature around it.
Borders that are debated: the German-Polish case
After the Second World War, in 1945, Poland's territory was shifted west. The new line followed the Oder and Neisse rivers. Millions of Germans had to leave the lands east of it, and Poles were settled there, many of them also moved from areas in the east.
For decades the line was in doubt. The border was gradually recognised through agreements: East Germany in 1950, West Germany in the Treaty of Warsaw in 1970, and the reunited Germany in a final treaty in 1990. Since both states joined the European Union and the Schengen area, people cross it today without passport checks.
The lesson: a border becomes firm when both sides sign a treaty and other states accept it, and over time shared membership of a group can soften it.
Borders at sea: the law of the sea
Seas also need rules. The United Nations Convention on the Law of the Sea (UNCLOS), agreed in 1982, divides the sea measured from the coast. A nautical mile is 1.852 km.
| Zone | Distance from coast | What the coastal state may do |
|---|---|---|
| Territorial sea | up to 12 nautical miles (about 22 km) | Full control, but ships of others may pass peacefully |
| Contiguous zone | up to 24 nautical miles | Customs, health and immigration checks |
| Exclusive economic zone (EEZ) | up to 200 nautical miles (about 370 km) | Sole right to fish, drill and make energy; ships may still sail |
| High seas | beyond the EEZ | Open to all states |
Disputes happen when coasts are close (zones overlap) or when states argue whether a rock is an island that earns its own zones. They are settled by talks or by courts.
Cross-border spaces
A border also brings people together. Cross-border spaces are places where life continues across the line:
- Commuters: workers who live in one state and work in another each day.
- Shared rivers and nature parks: states plan water and wildlife together.
- Joint regions and trade zones: for example, border regions inside the European Union that share transport and hospitals.
- Markets and festivals along the line, and families who live on both sides.
- Special arrangements: the 2015 India-Bangladesh exchange of enclaves gave residents the right to normal services.
These spaces show that a border can be both a barrier and a bridge. In the 3D free play, switch the cross-border link on and watch people cross.
Try it: draw a border and test it
On paper, draw a river, two hills and 12 small houses in two colours. First draw a border that follows the river. Then draw a straight line with a ruler and count how many houses of each colour are on each side. Which border cuts fewer groups? Now add a bridge. Who would use it? Compare with the 3D slider.
Key formulas and definitions
- Border: a line separating the land and rights of two states
- Natural border: follows a river, ridge, lake or coast; ruled border: straight line on a map
- Limes: Roman controlled frontier with forts, roads and crossing points
- Berlin Conference: 1884 to 1885, rules for claiming Africa, no African ruler present
- Korean DMZ: ceasefire strip about 250 km long and 4 km wide (1953)
- UNCLOS 1982: territorial sea 12 nm, contiguous zone 24 nm, EEZ 200 nm, then high seas
- 1 nautical mile = 1.852 km
Worked examples
1. Give two reasons why the number of borders has grown since 1945.
Colonies in Asia and Africa became independent states (decolonisation), and big states broke up, such as the Soviet Union and Yugoslavia in 1991. Groups wanting self-rule also formed new states.
2. A state claims waters up to 200 nautical miles. Convert to kilometres and name the zone.
200 x 1.852 = 370.4 km, about 370 km. This is the exclusive economic zone (EEZ): sole right to fish and drill, but ships may still sail through.
3. Why can a straight border drawn by outsiders cause trouble later?
It ignores where groups live. It can split one people between two states and join groups that are not friendly, which can lead to tension and migration.
4. Explain how the Roman limes was different from a sealed wall.
It had forts, watchtowers and roads for watching and moving fast, plus crossing points where trade was taxed. So it controlled movement instead of stopping it completely.
5. How did the German-Polish border become firmly recognised?
Through treaties: East Germany in 1950, West Germany in 1970, and united Germany in 1990. Later both states joined the EU, and checks at the line ended.
Common mistakes
- Thinking natural borders are always peaceful. People live on both banks, and rivers move.
- Thinking a border is the same as a wall. A border is a legal line; it may be open, guarded or fenced.
- Mixing up the sea zones: territorial sea is 12 nm, EEZ is 200 nm, and ships may still sail in the EEZ.
- Saying the Berlin Conference 'divided Africa' on its own. It set rules, and the actual lines were drawn over the following years by treaties between the powers.