Throughout history nations have made considerable efforts to find solutions to defend themselves against external threats. Perhaps the best example would be the creation of vast and expensive defensive lines to protect their countries from invasion or infiltration. Yet despite the considerable time and resources that have been expended into such endeavors nearly all without exception have inevitably failed to accomplish their ultimate goals. Defensive lines throughout history have typically failed to safeguard countries from external aggression.
If we look at defensive lines in military history they typically fall into two categories; those designed to stop conventional attacks by an invading army, and those designed to stop insurgents, bandits, or terrorists, from infiltrating sovereign territory. In the case of the former they have almost always failed to protect their respective countries while in the latter their success is often limited to the short term. Obviously the first thing to consider is how defensive lines are supposed to work.
Firstly, it should be noted that defensive lines are an inherently passive means to protect a country. They are designed as a physical means to prevent an enemy from invading or violating a very specific geographic location. The supposed logic behind their construction is that either the enemy would try outflanking the defensive line, thus allowing the defender to concentrate his forces against the attacking force, or the aggressor will be forced to attack the defensive line and play right into the defender’s hand. While this seems self evident and simple in theory, few things in military theory translate smoothly into practice.
In the case of constructing defensive lines in counter-terrorism and counter-insurgency the primary focus is decreasing terrorism from external forces in the former and limiting aid to insurgents already inside friendly territory in the latter.
While no expert would challenge the assertion that a defensive line can protect vital territory and offer the defender some degree of strategic options it is usually the case that elaborate defensive lines inevitably lead to a defensive attitude. And herein lies the quintessential flaw of defensive lines; they promote passiveness, intentionally or not, and concede initiative to the enemy. Perhaps the best example of this would be the “Maginot mentality” that afflicted the French army during the “Second World War.” The French, who had suffered six million casualties during “World War One,” constructed the Maginot line to deter another German invasion. However, despite being one of the great engineering marvels of the 20th century, the German air force flew over it and the German army outflanked it by going through the supposedly impenetrable Ardennes forests. While it took more than six years to build the Maginot line, it only took the Germans six weeks to conquer France.
Perhaps, and as absurd as it sounds, the majority of times defensive lines have failed is when they are simply outflanked and the defenders (having a mostly passive disposition) are unable to react effectively. Some of the time the defenders had built a defensive line to a certain length and then relied on supposedly impassable terrain, neutral borders, or sheer distance to do the rest. There are too many examples to cite but obvious ones include the aforementioned Maginot line, the Metaxas line in Greece, the French border fortifications before the “First World War,” and the Saddam Line.
Regarding the Metaxas line the Greeks built it to protect against a Bulgarian invasion, but when the Germans invaded Greece in 1941 they outflanked it by going through Yugoslavia. The Franco-German border fortifications prior to 1914 were likewise rendered redundant by the “Schlieffen plan” that by passed them by going through neutral Belgium at the start of the “First World War.” As the for the Saddam line the Iraqi forces simply thought that coalition forces would get lost in the desert as they had before them. Unfortunately for the Iraqis the advent of GPS made the task of outflanking the Saddam line child’s play.
Even defensive lines that cannot be outflanked, and are manned by competent soldiers can be defeated. In these situations it is usually a case of the attacker concentrating enough numbers and firepower and breaching part of the line. While this often results in disproportionate casualties for the attacker, a successful breach usually renders the whole line useless as the rest of it is then open to being bypassed or flanked. This highlights perhaps the biggest liability of defensive lines; they are inherently passive and are only effective at the points at which they are attacked. While perhaps the best that can be hoped from defensive lines is that they provide a trip wire to slow enemy forces to allow the defender to concentrate their reserves for a counter attack, all too often they are expected to halt the enemy almost exclusively by themselves.
Perhaps the best example occurred during “World War 1”, arguably the conflict most associated with the power of the defense, when the Germans relied upon the “Siegfried line” to protect their occupation of north eastern France. While it certainly withstood many assaults it was breached twice relatively easily by well executed British attacks in 1917 and 1918. During the former the British were unable to exploit the breach due to a lack of sufficient reserves, but in the latter the successful breach unhinged the whole line and the Germans were pushed back and forced to accept a humiliating armistice. This was against perhaps the most powerful defensive line in history up to that point and backed by well trained and seasoned troops.
Another poignant example would be the multiple defensive lines the Germans held in Italy, especially the Gustav and Gothic lines, and the Atlantic Wall that was supposed to repel an allied invasion of France, during “World War 2.” Keeping in mind the natural defenses the Italian peninsula offers, and the skill and tenacity of the German soldiers, these should have been ideal defensive lines. Indeed, the allies only breached these defenses after long and costly battles, especially around Monte Casino. However, numbers, firepower and stubbornness can, and often does, eventually succeed and the German defensive lines in Italy were all ultimately overrun. While one could argue that the allies only succeeded due to their material advantages, it should be born in mind that 99 times out of 100 it is the weaker adversary (at least in terms of numbers and resources) in any real, or potential, conflict that builds defensive lines, and it should not come as a surprise that their enemies are willing to use their superiority in order to defeat them. Yet to be fair to the Germans it could be argued that they constructed such defensive lines in Italy to delay the allied advance up the Italian boot, not to stop them indefinitely.
As for breaching the Atlantic wall the allies benefited from overwhelming firepower, meticulous planning and a brilliant deception plan that led the Germans to believe the invasion was supposed to take place in the Pas-De Calais region. Additionally, besides the fact the Germans simply did not have the time, or resources, to adequately fortify the whole Atlantic coast of occupied Europe, the German high command doomed any chance of repelling the allied landings when they failed to concentrate their panzer divisions near the beaches of the most likely landing sites.
An almost amusing example of how easily supposedly strong fortifications can be breached would be the Egyptian conquest of the Bar-Lev line guarding the east bank of the Suez Canal in 1973. The Israelis had constructed a massive sand beam nearly 100 feet tall almost running the entire length of their side of the canal. It was said to be so strong that some armchair generals believed it could only be breached by nuclear weapons. In the event the Egyptians defeated the formidable sand beam in a matter of hours by simply watering it down with high pressure hoses!
However, it can be assumed there are examples of defensive lines succeeding outright in conventional warfare. Yet, admittedly the author is only familiar with one example and that is the Lines of Torres Vedras guarding the British presence in Portugal during the “Napoleonic wars.” However the lines of Torres Vedras succeeded due to very specific conditions; conditions which other defensive lines seldom meet.
Firstly, the defensive lines could not be flanked because they were built from coast to coast and the British navy controlled the sea lanes. Secondly, the French army in Spain did not possess the necessary firepower to breach its powerful fortifications. Thirdly, the British had conducted a scorched earth policy while retreating through Spain and the French army was suffering from significant shortages. Lastly, the front on which the lines were constructed was relatively narrow which allowed the British and Portuguese forces to man the defenses in strength. Needless to say such conditions have seldom been met in the history of warfare and this probably helps explains why so few defensive lines have been as successful as those of Torres Vedras.
A seldom mentioned consideration regarding the inherent liabilities of defensive lines is that they tend to be inordinately expensive to build. While they usually look impressive one wonders how many planes, tanks, artillery pieces, or other critical weapons of war could have been built in their place. Indeed, while touring the Maginot line near the beginning of “World War 2” Field Marshal Alanbrooke was fascinated by such a marvel of engineering but was ultimately unimpressed saying it “gave me but little feeling of security, and I consider that the French would have done better to invest the money in the shape of mobile defenses such as more and better aircraft and more heavy armored divisions than to sink all this money into the ground.”
However, if defensive lines mostly fail in conventional warfare, they can be quite successful, at least in tactical terms, in counter-insurgency and counter-terrorism. Indeed, given that insurgents and terrorists are by nature usually weaker in numbers and firepower than their opponents they find it nearly impossible to breach, let alone neutralize, defensive lines. While admittedly defensive lines have been used less extensively against irregular opponents, not least because it is much easier for them to infiltrate across long borders, or via the coast vs. divisions of soldiers, when they have been used they generally have a better track record then those designed to stop conventional attacks. The usual, though not exclusive, prerequisites for this success are obvious; relatively short borders, open terrain, and well armed and motivated forces patrolling the area in question. Needless to say, these are conditions that are seldom met as successful insurgent movements tend to thrive in countries with porous borders, difficult topography and corrupt government and military personnel.
While it can be exhausting looking for examples of defensive lines that have succeeded in conventional warfare, there are plenty of examples regarding the success of defensive lines in asymmetrical warfare, at least in a tactical sense. The Morice Line during the “Algerian War,” Hadrian’s Wall, Chiang Kai-shek’s use of Block House warfare against the Communists during the “Chinese Civil War,” and the barriers erected by the Israelis to surround the Gaza Strip and West Bank were all unequivocally successful in severely reducing the capabilities of insurgents, terrorists, freedom fighters, or whatever terms people label such irregular movements depending upon their political biases or sympathies.
The Morice line was built on the Algerian-Tunisian border by the French during the “Algerian War” to stop the vast flow of weapons, men, and supplies reaching the F.L.N. (an insurgent movement dedicated to liberating Algeria from French rule) fighting inside Algeria. While the French usually have a bad reputation, mostly deserved, regarding their policies aimed at quashing the F.L.N. insurgency, the construction of the Morice Line, and an equivalent line along the Moroccan-Algerian border, proved to be an unqualified tactical success. Indeed, these defensive lines all but cut off the F.L.N. from the outside world and quashed any chance of them defeating the French militarily inside Algeria.
Hadrian’s wall was also successful as it stopped barbarians from invading Rome’s colony in Britain. As the border between the colony and barbarian territory was not very long, and as the Romans had naval supremacy, it was not unduly hard to plug this hole in Rome’s territorial expansion. While it is not clear regarding the ultimate purpose(s) of the wall, it is clear that no major hostile forces infiltrated Rome’s British colony as long as it was adequately garrisoned.
Chiang Kai-shek’s use of block house warfare in the “Chinese Civil War” is admittedly a bit different regarding defensive lines as the defenses were not located on any border and were not meant to be permanent but the same principles regarding its use applies. Instead of trying to keep insurgents out of specified territory, the plan was for Chinese nationalist forces to enter communist areas, build block houses and defenses, secure the area, then move further into the interior and repeat this process again and again. The Chinese nationalists did this on all sides of the communist region to surround the whole area, then used the multiple layers of blockhouses and defenses to squeeze the communists and limit their mobility. This was significant because whereas conventional forces fighting irregulars rely upon numbers and firepower to win engagements, irregulars use their usually superior knowledge of the terrain and maneuverability to engage in surprise attacks against soldiers to compensate for their material disadvantages. Isolated from other insurgent forces, cut off from their support base, and at a distinct advantage when fighting the well placed, numerically superior and better equipped nationalist forces, the Chi-Coms (Chinese communists) were eventually forced to break out of the encirclement and conduct a desperate retreat of more than 6000 miles to north eastern China.
Likewise the barriers built to stop terrorist infiltration from the Gaza Strip and the West Bank to Israel have proven to be a significant tactical coup. Given the open terrain, the relatively short borders, and the considerable amount of men and resources the Israeli Defence Forces have invested in the project, it is no surprise that terrorist attacks launched from Gaza and the West Bank have fallen to virtually nothing. Whatever the moral or humanitarian effects these walls have had regarding the Palestinian populations of these territories (and they are not inconsiderable) there is no doubt the barriers have accomplished their stated aim.
However, while the author has stated that defensive lines in asymmetrical warfare can have exceeding good tactical returns, he also noted that they are not as successful in the long term, or in strategic terms. Once this implication has been considered, it is no surprise that just as in conventional warfare defensive lines are ultimately unsuccessful in irregular conflicts as well.
Looking at the last four examples, one sees that the insurgent/terrorist movements in all these cases were not decisively defeated at all. The F.L.N. held on in Algeria until the ultranationalist Pied Noires and overly militant French army shot themselves in the foot, and alienated so many Frenchmen regarding their brutal behavior, that even the proud Charles De-Gaulle decided to give up Algeria. Hadrian’s wall did nothing to stop the growing decadence in the Roman Empire that ultimately led to the Romans abandoning their British colony. Even the 6000 mile retreat of the Communists in China was not enough as the “Sino-Japanese conflict” severely degraded the Nationalists and ultimately strengthened the Communists so much they won the military contest after the “Second World War.” As for Israeli success regarding her walls surrounding the West Bank and Gaza, it may have more or less stopped border intrusions, but did little to stop her enemy’s from acquiring rockets and missile that have led to two significant wars, in Lebanon in 2006 and Gaza in 2009, let alone crush the said organizations bent on her destruction.
Inevitably, this is a consequence of the inherent differences regarding victory in conventional war vs. victory in asymmetrical warfare. While victory in the former is usually the result of military means (taking a capital city, destroying an army, cutting off a force’s lines of communication, etc.) victory against terrorists or insurgents is usually the result of more economic, political, or diplomatic considerations. These usually involve winning the relevant populations’ hearts and minds, addressing grievances, and improving their political and economic standing. Or alternatively, a disproportionately bloody solution can work if the population believes the assailant will do anything necessary to quash dissent. Britain’s successes in the “Malayan Emergency” and in Northern Ireland are examples of the former approach, while the German genocidal tendencies in Namibia and Syria’s massacre of 10s of thousands of its own citizens in Hama in 1982 are examples of the latter approach. Needless to say the former solution is suitable for democracies, while the latter solution is used almost exclusively by authoritarian and totalitarian regimes. Either way it is apparent that while defensive lines can serve a purpose regarding such means, they are obviously not decisive in themselves.
None of this is to suggest that defensive lines or fortifications do not have an important part in warfare, conventional or asymmetrical. In the case of acting as a so called “trip wire” they can fragment an enemy’s advance of at least determine their likely axis of advance. Additionally, they are extremely useful, in multiple layers, at delaying a strong advance until a counterattack can be organized. This refers to the concept of “defense in depth,” and has been used to great effect in instances such as the “Battle of Third Ypres” in “World War 1” and the “Battle of Kursk” in the “Second World War.”
No, the point at which defensive lines become counter-productive is when they are expected to perform miracles and defeat whole armies and insurgents by themselves. Rather than being seem as either trip lines or a means to delay, they become the hope of the nation and contribute to a bunker, or “Maginot,” mentality. It should be clear that the author does not think defensive lines, even overly expensive ones such as the Maginot line, are useless. Had the French constructed the line to the English Channel or at least to cover the Ardennes forest they probably would not have been defeated by the Germans, or at least would have held out longer than six weeks. Yet besides such defenses the French needed to be bold and offensive minded and concentrated their forces for an attack on the Germans as the Maginot line allowed their army to do so.
Unfortunately, and ironic as it sounds, this is what defensive lines are supposed to accomplish. They are supposed to substitute concrete and barbed wire for men so a nation can concentrate its army and fight boldly against the enemy, and not be expected to serve as a rampart to be attacked in force by a foe with any common sense. Yet perhaps it is unsurprising that nations that put so many resources “into the ground,” as Field Marshal Alanbooke would put it, should not be expected to have the most offensive spirit when it comes to warfare. Allowing an army to concentrate its forces more effectively, along with the other uses stated above (serving as a trip line, fragmenting an attack, or delaying the enemy) is what should realistically be expected of defensive lines 99 times out of 100.
In all of these means defensive lines have an important purpose, but when they are depended upon to stop a powerful and innovative enemy on their own, or stop terrorism or insurgency cold, the historical record regarding their success should be labeled as “not good enough.”