While The Tunnel on PBS shows professional tensions between the British and French detectives co-investigating a serial killer’s crimes, at least their countries are on friendly terms (and during the series’ creation, both were solid members of the European Union). What’s more: Great Britain and France only have to share an earthbound border beneath the seabed of the English Channel.

National borders are the scene of criminal activities, senseless tragedies and government-led transgressions — most famously, that of invasions and war.

Here are just a few examples of the trouble with borders throughout time and place.

The Start of World War II: German-Polish Border

The Nazis concocted a fake border skirmish in order to justify to the world Germany’s invasion of Poland on September 1, 1939. This “false flag” project was one of nearly two-dozen ruses along the Polish border that formed part of Operation Himmler, named for Nazi leader Heinrich Himmler.

On the evening of August 31, Nazi S.S. troops donned Polish uniforms to stage a faked invasion of Germany. They damaged a radio installation on the German side of the border, and offered German propaganda cameras more evidence of a border skirmish in a most grotesque way. Bodies of dead concentration camp prisoners were dressed in Polish uniforms and scattered to further suggest a Polish invasion. The Nazis accused Poland of initiating this act of aggression, and thus justified the German invasion of the neighboring country.

The Cold War: The Berlin Wall

The Berlin Wall was built in August 1961 by the Soviet-backed East German government. The purpose? To prevent East German citizens from fleeing to West Berlin, a free city occupied by the Western Allies of World War II, and part of West Germany. The Wall effectively surrounded the city of West Berlin and in addition to its concrete wall component, the formidable border included a wide swath of land, or waterway at times, known as the “no-man’s land” which in parts had mines, guard dogs and vehicle barricades. The no-man’s land belonged to East Germany and was heavily guarded. One would be shot without warning if found there.

According to the Berlin Wall Memorial Foundation, 100 East German fugitives were killed or died at the Wall between 1961 and 1989. Thirty people from both the East and the West who were not even intending to flee were shot or died in an accident at the Wall.

Among those who died were five children between the ages of five and eight, from West Berlin.

Each child had accidentally fell into the Spree River that in some stretches, was part of the borderland. The children did not immediately drown and witnesses were often present. Yet West Berliners did not dare enter the watery border for fear of being shot by the East German border control; West Berlin police and fire officials had no permission to enter the waters; and East German chose not to respond, or feared being shot by their own compatriots for entering the no-man’s area.

It wasn’t until 1975 that the East and West Berlin governments reached an agreement that would allow them to peaceably respond to persons in distress on the waterways.

Drug Smuggling Tunnels: Mexican-US Border

According to US Immigration and Customs Enforcement, federal authorities have detected more than 75 cross-border smuggling tunnels, most of them connecting Mexico to California and Arizona, in the past five years alone. Tunnels between Tijuana, Mexico, and the Otay Mesa neighborhood of San Diego, California, are common and the longest drug smuggling tunnel yet — 800 yards — was discovered in April 2016.

According to the Los Angeles Times, sheriff deputies stopped a truck coming from that tunnel site with more than 13,000 pounds of drugs on April 15, 2016.

Protecting the Environment: Haiti-Dominican Republic Border

How can a country protect its environment when it shares the same island with another country? French-speaking Haiti and Spanish-speaking Dominican Republic share the Caribbean island of Hispaniola, the second largest in the Caribbean after Cuba and the tenth-most populated island in the world. Haiti, a country where poverty, governmental instability and reliance on charcoal has reigned, had become 98% deforested by 2012, while Dominican Republic began restoring its depleted rainforests in the 1960s.

According to the Borgen Project, in 2013 Haitian President Michel Martelly launched a campaign to plant 50 million trees a year.
In the meantime, Haitians are crossing into the Dominican Republic, particularly to the cloud forest of Sierra de Bahoruco National Park, to essentially poach its trees. A new documentary to hit the festival circuit this year, Death by a Thousand Cuts, examines deforestation and Haitians’ illegal crossing into the Dominican Republic to claim more trees for charcoal sales in their own country.