dividing walls:
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.”
(...) 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.
(...) 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.
(...) 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.
(...) 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.
(...) 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.

western sahara background:
Western Sahara, like East Timor, was a European colony until the mid-1970s. In a landmark 1975 ruling, the International Court of Justice dismissed Morocco's historical claims to Western Sahara and instead supported the Sahrawis' right to self-determination. The UN Security Council and Secretary General have both reiterated their support for a solution that provides for self-determination, which would entail a vote including, but not limited to, the option of independence.
(...) Though the Ford, Carter, and Reagan administrations had provided material support for Morocco's invasion and occupation of Western Sahara from 1975 to 1991, the first Bush and Clinton administrations maintained a hands-off policy toward the early UN referendum process (1992-1996). Indirect, high-level U.S. involvement -- in the form of former U.S. Secretary of State James Baker -- began in 1997. However, Baker's seven-year engagement was sabotaged, on the U.S. side, by larger geo-strategic concerns: Morocco's role as an ally in -- and after May 2003 a site of -- the war on terror.
(...) The stalemate in Western Sahara was originally achieved on the battlefield during a 16-year war pitting Western-supported Morocco against the Algerian-backed Sahrawi guerrillas of the Polisario Front.
(...) The idea was to grant Western Sahara four years of autonomy as a kind of trial period and then hold a final status referendum. The choices would be autonomy, integration with Morocco, or full independence. To sweeten the deal for Rabat, Baker proposed that non-Sahrawi Moroccan settlers could participate in the vote. With Moroccan colonists outnumbering the native Sahrawi population by as much as two-to-one, it came as quite a shock that Rabat rejected the proposal as soon as Polisario accepted it. Baker worked with Morocco for another year, but all of Rabat's counter-proposals demonstrated a deep unwillingness to compromise on the most fundamental issue, the right of self-determination
(...) Growing in militancy, the Western Saharan independence movement has spawned its own intifadah, a decentralized, youth-led, anti-Moroccan protest movement in the occupied region. The Sahrawi heroes of this struggle are former political prisoners who have become unashamed nationalists. Many Sahrawis living under Moroccan administration are no longer afraid to speak their mind about the Moroccan occupation, for which they suffer regular beatings and imprisonment. The flag of Polisario, once unseen in Moroccan-controlled areas, is now a ubiquitous symbol of Sahrawi resistance. The only internal feedback that Polisario's leaders are receiving is toward greater confrontation not compromise.
(...) Instead, the determinant reality is that Western Saharan nationalism is growing, not diminishing. Thirty years of exile (for the Sahrawi refugees in Algeria) and socio-economic marginalization (for the Sahrawis under Moroccan administration) have strengthened their resolve, not diminished it. In the streets of Western Sahara, an escalating dialectic of violence is being played out day by day. Protest meets repression meets counter-protest meets police retaliation in an endless cycle. How much longer can Polisario's leaders justify to their constituents, without losing all credibility, the maintenance of a cease-fire that is now considered pointless by many nationalists?