TIJUANA, Mexico - What do Tijuana, Baghdad and Jerusalem have in common?
They all have walls that divide neighbors, cause controversy and form part of an array of physical barriers around the world that dwarf the late, unlamented Iron Curtain.
There are walls, fences, trenches and berms. Some are reinforced by motion detectors, heat-sensing cameras, X-ray systems, night-vision equipment, helicopters, drones and blimps. Some are still under construction, some in the planning stage.
When completed, the barriers will run thousands of miles, in places as far apart as Mexico and India, Afghanistan and Spain, Morocco and Thailand, Malaysia and Saudi Arabia, and Iraq.
They are meant to keep job-hungry immigrants, terrorists and smugglers out, thwart invaders, and keep antagonists apart.
Their proponents cite the proverb "Good fences make good neighbors" but critics say they are a paradoxical result of globalization in so far as goods and capital can move freely but migrants cannot.
By an irony of history, the United States -- the country that hastened the fall of the Berlin Wall in 1989 -- has emerged as a champion wall builder.
The latest wall to divide city neighborhoods went up in Baghdad in April, built by American soldiers using 12-foot (3.7-metre) high grey concrete slabs weighing more than six metric tons each. The 3-mile-long construction separates a Sunni Muslim district from a Shi'ite area.
It provoked protests from both communities and Shi'ite cleric Moqtada al-Sadr termed it "racist."
The wall that snakes through Jerusalem to seal off the eastern (Arab) part of the ancient city from the West Bank is of similar construction and inspires similar charges.
In contrast, the people of the Mexican border city of Tijuana have become resigned to the wall of thick, rusty corrugated metal that runs from the surf of the Pacific beach up and down the California hills, separating them from the U.S. city of San Diego. (The official border crossing is the world's busiest -- around 17 million cars and 50 million people a year.)
Further inland, the wall turns into a 17-foot (5-meter) fence, with metal mesh so fine prospective climbers cannot get their fingers through, and an overhanging portion to make scaling even more difficult. It stretches east for 14 miles.
ARE WALLS EFFECTIVE?
The United States is planning to build a 700-mile double-layered fence along part of its 2,000-mile border with Mexico under the 2006 Secure Fence Act. Proponents point to Tijuana and argue that physical barriers are effective in keeping unwanted foreigners out.
Since the attacks on New York and Washington of September 11, 2001, anti-immigrant groups in the United Sates have linked illegal immigration with security concerns, and political pressure for tighter border controls grew exponentially.
The Tijuana wall stopped the "banzai runs" of groups of up to 50 illegal crossers who swarmed past border guards in the knowledge that at least some would get past. Before the wall was built, arrests totaled around half a million a year, and have steadily dropped to around 130,000 last year.
But opponents of walling off the United States point to the unintended consequences: a booming industry in building tunnels under the wall (the longest to date, almost half a mile, was discovered in San Diego last year) and in forging identity documents.
And as would-be crossers detoured around the fence and trekked across the Arizona desert instead, the death toll rose steadily, to an average of nine a week.
Latin American politicians in general and Mexicans in particular see the border wall as an affront, and a departure from the philosophy that prompted then President Ronald Reagan, standing before Berlin's Brandenburg Gate, to challenge his Soviet counterpart to "open this gate ... tear down this wall."
Two years later, the wall fell, and, not much later, so did what remained of the Iron Curtain, the lethal system of walls, fences and minefields that sliced 2,500 miles through Europe and divided countries under communist rule from capitalist democracies.
Many of the ruses used when the Iron Curtain was still up -- hollowed out hiding spaces in cars, tunnels, hook ladders -- are still used now. Then, successful crossers were hailed as heroes of freedom. Now they are seen as a threat or a burden.
WALLS TO CEMENT TERRITORIAL CLAIMS
While security and immigration control are the most frequently cited reasons for building border walls, politics play a key role in some countries. In others, fortifications serve to translate territorial claims into concrete facts on the ground.
That applies to one of the least known but longest border barriers of modern times, built by Morocco in the 1980s to curb attacks by the Western Sahara independent movement, Polisario, on territory it claims for itself.
It lies behind a set of walls some 1,700 miles long and 10 feet high made of earth, rock and sand built in the 1980s.
The wall is defended by thousands of Moroccan troops and fortified by bunkers and fences, barbed wire and landmines -- between 200,000 and several million of them, depending on who does the estimating.
To hear Palestinians and United Nations officials tell it, the grey concrete wall that splits Jerusalem from the West Bank and the fences and trenches that run through the West Bank have as much to do with Israeli expansionism as with the stated, and largely successful, purpose of keeping suicide bombers out of Israel.
The West Bank berms, barriers and fences are almost twice as long as Israel's internationally recognized borders and run in a way that make major Jewish settlements in the West Bank a part of Israel.
Israelis who oppose the occupation of the West Bank, as well as foreign critics such as former U.S. President Jimmy Carter, talk of "apartheid walls".
Israel's wall has been a persistent target of Arab criticism but Arab countries have built or are building walls themselves.
Saudi Arabia has quietly invited bids for a 550-mile high-tech fence -- complete with sensors, night vision cameras, face-recognition software, barbed wire -- to seal off its border with Iraq.
CONTAINING IRAQ CHAOS
According to U.S. defense contractor sources, the project will cost several billion dollars and was prompted by fears that growing anarchy and unrest in Iraq will spill into Saudi Arabia.
The Saudis stopped work on a barrier along their border with Yemen -- made up largely of huge pipelines filled with concrete -- after Yemeni complaints three years ago.
Another neighbor of Iraq, Kuwait, has already sealed its border with electrified fences, berms and a two-meter deep trench running along the 135-mile (217-kilometer) dividing line, according to a senior Kuwaiti diplomat in Washington.
There is constant aerial surveillance of the line, across which Iraqi tanks rolled in the 1991 invasion of Kuwait.
East of the Arabian Peninsula, ambitious projects are underway to control movement between India and Pakistan; India and Bangladesh; and Pakistan and Afghanistan.
Almost invariably, governments that decide on physical separation from a neighbor predict that it would reduce tension but, at times, that remains wishful thinking.
In April, for example, a firefight broke out between Afghan and Pakistani troops after the Afghans tried to tear down parts of a fence running through a tribal area.
Pakistan started building a fence along part of the 1,500-mile (2,500-kilometer) border under U.S. pressure to close the routes of Taliban fighters heading to Afghanistan to join the war against U.S. and multinational forces.
In Europe, two of the most infamous walls -- the remnants of the Berlin wall and the "Peace Wall" in Belfast -- have become tourist attractions. But Spain has built double fences 10 to 20 feet high and topped with razor wire around its wealthy enclaves of Ceuta and Melilla in Morocco to keep immigrants out.
The fences have had an effect similar to the walls on the border between the United States and Mexico: would-be immigrants from poor countries looked for other ways to reach a rich country.
Stepped-up Spanish coastal patrols and better radar systems prompted African migrants to make riskier voyages to the Spanish-owned Canary Islands. Hundreds have drowned.
If history is a guide, no border fortification can seal off a country entirely. Even the mother of all walls, the Great Wall of China, at around 4,000 miles the longest border wall ever built, failed to keep out the northern barbarians against whom it was meant to protect.
Additional reporting by Robert Birsel and Simon Cameron-Moore in Islamabad, Kamil Zaheer in New Delhi, Tom Pfeiffer in Rabat, Sheikh Mushtaq in Srinagar, Daniela Deasantis in Paraguay and Tim Gaynor in Phoenix
© Reuters 2007