Just like any security system, from asymmetric encryption to a steel military weapons vault, you can't make something perfectly secure. You can only make it difficult and time-consuming to breach the target. https://www.internationalvault.com/images/standards/class-a-...
The concrete barriers in Iraq can be and have been breached. https://www.csmonitor.com/World/Middle-East/2016/0430/Pro-Sa...
And that's the crux of the issue: a militarized Green Zone has forces ready and able to respond when a breach attempt is detected, whereas remote New Mexico desert does not. The timescale of an unlawful entry event is a total mismatch for the amount of delay this particular security measure will introduce in an immigration context -- it's like using single-pass DES for strategic intel against an adversary with a botnet.
From what I understand from reading a lot of stuff (including Sebastian Junger's book War), the barriers were needed because of regular and persistent attacks with bombs and gunfire, and I haven't heard even the most alarmist pro-wall person claim that level of violence from illegal immigrants.
99% Invisible just released an episode about the tunnels used in smuggling drugs from Mexico into the US - https://99percentinvisible.org/episode/the-tunnel/. Basically, the tunnels cost $1-2M or more but paid off in a matter of weeks. Getting past concrete barriers in Iraq may have been strategically valuable but didn't have a business model.
I would imagine that climbing the barriers puts you in a very undefended position for at least a couple minutes.
Walls create an impedance. Building a tunnel is a lot more effort (time, equipment, labor, etc.) than walking in. Employing a ladder is exposure; ladders are really hard to conceal.
People that claim a border wall is necessary and will be effective, such as the National Border Patrol Council, the union of border patrol officers, aren't actually ignoramuses. They don't believe or claim a wall is a perfect passive deterrent. It is a force multiplier, and like the Sadr City wall, will be effective while it is patrolled, maintained, etc.
A difference is that along the non-urban sections of the US-Mexico border, a wall needs to prevent individual persons from crossing. In Baghdad, the reason for division was to prevent large munitions, vehicle borne IEDs, and scattered gunfire.
In summary, walls can be effective, and they exist where needed along the US-Mexico border. A grand, glorious, wall in the middle of nowhere will not be helpful.
> The barriers used to form the walls were named after American states to denote their progressive size. The smallest, Jersey barriers (three feet tall; two tons), were used to block roads and slow traffic approaching checkpoints. Medium to large barriers—Colorado (six feet tall; 3.5 tons), Texas (six feet, eight inches tall; six tons), and Alaska (twelve feet tall; seven tons)—were used to construct checkpoints and protective walls around markets, mosques, and other areas where crowds were being targeted by bombs and shootings. The Texas barrier, due to its width and ease of transport, among other reasons, was predominately used to create the safe neighborhoods. But it was the massive T-walls that were used to create coalition and ISF bases and to maximize protection and prevent infiltration. Similar in size to Alaska barriers, the massive twelve-foot-tall, six-ton T-wall, with its interconnecting edges, created an effective barrier.
Curious how folks interpret these statements as reinforcing or undermining their positions on the US Border Wall debacle. Is it a possibility that POTUS, upon hearing reports similar to this from Iraq, might be likely to want to reuse the approach?
Conversely, why is this effective in Iraq? Can opposition forces not build tunnels or lay ladders over these walls?