Terrorism as a term of art was first used by journalists and letter writers during the middle phase of the French Revolution  in 1793-4. The Jacobin faction  of the Committee of Public Safety  was trying to consolidate their hold on power, and so in order to eliminate potential counter-revolutionaries and rival factions, began a program of massive arrests, show trials , and executions. This time period is known today as the Reign of Terror. 
When a journalist asked Jacobin leader Georges Danton  what faction was controlling the mobocracy  government of the day, the Committee of Public Safety, he replied, 'the same as always. Terror rules here now' (Fromkin 188). Danton was describing a situation where the rule of terror prevailed. A situation existed where anyone was subject to arrest, torture, trial, imprisonment, or execution for no apparent reason. An ideology as it were, based not upon ideas but a generalized condition of fear for your life every waking minute. And thus the concept of terrorizing people as a means of political suasion entered the modern age.
The emergence of nominally democratic parliamentary states in the 19th and 20th centuries led to a profound change in terrorism. Modern governments have a continuity that older monarchies did not. Terrorists found that the death of a single individual, even a King or Czar, did not necessarily produce the policy changes they sought. Terrorists reacted by turning to an indirect method of attack. By the early 20th Century, terrorists began to attack people previously considered innocents to generate political pressure (Fromkin 192-3).
These indirect attacks created a public atmosphere of anxiety and undermined confidence in government. Their unpredictability and apparent randomness made it virtually impossible for governments to protect all potential victims. The public demands protection that the state cannot give. Frustrated and fearful, the people then demand that the government make concessions to stop the attacks.
Groups considering terrorism as a tactic must answer a crucial question: Will it induce enough anxiety to attain their goals without causing a backlash that will destroy the cause and perhaps the terrorists themselves? To misjudge the answer is to cause large-scale death and injury and set back the terrorists' own goals as well (NWC 66).
V.I. Lenin  understood what was involved in making the decision to employ terror as a tactic. Writing from exile in 1903, he commented on the decision to resort to terror tactics.
'In principle,' Lenin wrote,' we have never rejected, and cannot reject, terror. Terror is one of the forms of military action that may be perfectly suitable and even essential at a definite juncture in the battle, given a definite state of the troops and the existence of definite conditions' (Lenin 121).
The generations that have come to maturity in Europe and America since the end of World War II have asked only to bask in the sunshine of a summertime world: but increasingly they have been forced instead to live in the fearful shadow of other people's deadly quarrels. Cells of politically motivated operatives have disrupted everyday life, intruding and forcing their parochial feuds upon the unwilling attention of everybody else.
Too small to impose their will by military force, terrorist bands nonetheless are capable nowadays of causing enough damage to intimidate and blackmail the governments of the world. Only modern technology makes this possible. Easy access to small arms, explosives, the worldwide reach of the mass media and the Internet, just to name but a few. Perhaps, over the horizon, biological and chemical weapons and the worst of all, nuclear weapons. The transformation has enabled terrorism to enter the political arena on a new scale, and to express ideological goals of an organized sort rather than mere crime, madness, or emotion.
To outward appearances, terror seems like a terrible undertaking. Why would anyone resort to it? Appearances, though, can be deceiving.
In what is known as asymmetrical warfare , the sides involved in the conflict are not equal. Insurgents of whatever stripe are rational to the extent that they realize that the larger forces of the state they are opposed to would quickly annihilate any formally organized military operation that they could mount.
Examples of this situation are the Hamas /Israel and the Irish Republican Army /UK conflicts. In both cases, ethnic minorities are waging war against a powerful, established state with full military and police capabilities. Any attempt at raising armed forces and waging a traditional military campaign would be doomed to failure.
And this humiliating state of affairs is what compels the seemingly irrational choice to use terror. The British forces in Belfast , Ireland and Israeli forces in Palestine and Gaza can move and operate at will. Other than small scale sniper attacks, roadside bombs or ambushes, the IRA or Palestinian independence groups are very limited indeed in the kind of operations that they can undertake against their occupiers. The UK forces and IDF  can move and shoot at will. So what to do then if you are an IRA or Hamas  commander?
If you are the oppressed minority, the conclusion is this: The government army and police can attack you and your family, associates, businesses and community-based institutions at will. At any time or place and for any reason. You and yours are 100% vulnerable to assault at any moment. There is no sanctuary, respite or peace available to you. Your enemies, though, can live in relative peace in their daily lives. You are always on edge and fearful and they have relative safety. Other than moral suasion, what leverage do the oppressed have to make the oppressor address their issues? What can they do?
The only compelling course is to redress the issue of safety. The weaker side reckons that if they can't live in safety, then neither can their oppressors. And so the point/counter-point spiral of violence and retaliation begins and continues until one side becomes exhausted.
Retaliatory collective punishments and increased levels of repression humiliate and oppress the insurgent population base further. The government-represented population must then spend an ever-increasing amount of money on military and security measures, which buy only temporary safety for them. The government and the insurgent commanders are then locked into a deadly and dangerous game of chicken to see who turns away first. And the civilian populations pay with their lives, limbs, and blood.
The rational terrorist leader thinks through his goals and options, making a cost-benefit analysis. He seeks to determine whether there are less costly and more effective ways to achieve his objective than terrorism (NWC 167).
To assess the risk, he weighs the target's defensive capabilities against his own capabilities to attack. He measures his group's capabilities to sustain the effort. The essential question is whether terrorism will work for the desired purpose, given societal conditions at the time. The terrorist's rational analysis is similar to that of a military commander or a business entrepreneur considering available courses of action (NWC 168).
The intelligence analysis staff of the Royal Ulster Constabulary , the police force for British-controlled Ireland , has developed this summation of the terrorist operational patterns.
'As commanders and staffs address terrorism,' the study says,' they must consider several relevant characteristics. First is that anyone can be a victim. Second, attacks that may appear to be senseless and random are not. To the perpetrators, their attacks make perfect sense. Acts such as bombing public places of assembly and shooting into crowded restaurants heighten public anxiety. This is the terrorists' immediate objective. Third, the terrorist needs to publicize his attack. If no one knows about it, it will not produce fear. The need for publicity often drives target selection: the greater the symbolic value of the target, the more publicity the attack brings to the terrorists and the more fear it generates. Finally, a leader planning for combating terrorism must understand that he cannot protect every possible target all the time. He must also understand that terrorists will likely shift from more protected targets to less protected ones. This is the key to defensive measures' (Divishi 112).
As in the video arcade game Whack-a-Mole , the military and security forces are in a constant state of crisis: As soon as they respond to one incident in one place, another incident happens somewhere else. While the state's forces are larger, better trained and armed, the terror cells are able to choose the time, place, and severity of the attacks against their chosen targets.
Modern terrorism offers its practitioners many advantages. First, by not recognizing innocents, terrorists have an infinite number of targets. They select their target and determine when, where, and how to attack. The range of choices gives terrorists a high probability of success with minimum risk. If the attack goes wrong or fails to produce the intended results, the terrorists can deny responsibility. The governments' advantages in resources, equipment, and manpower are often not enough to overcome this advantage the terrorists have.
'[a]n ambush is totally different from a battle. Let's say your squad is patrolling through a village just like it's done for the past two weeks, right? Everything's hunky-dory: the little old lady who sells veggies waves and smiles when you go past, the kids ask for gum, and you start to feel like a liberator. You're just turning a corner when there's a big boom and two of your buddies are on the ground screaming, two others are dead. You look around--where's the old lady? Where are all the smiling kiddies? A blast that big should've killed a dozen locals, but somehow the only casualties are your buddies' (Brecher).
But the terrorist can slip up, too. Terrorist groups with strong internal motivations find it necessary to justify the group's existence continuously. A terrorist group must terrorize. As a minimum, it must commit violent acts to maintain group self-esteem and legitimacy. Thus, terrorists sometimes carry out attacks that are objectively nonproductive or even counter-productive to their announced goal.
This is usually when the moderate elements on both sides have become marginalized for whatever reason, says Schlomo Divishi, a former member of the Israeli intelligence service the Mossad  (Divishi 148).
Odd as it may seem when viewed on CNN , the bombings, kidnappings, assassinations, hijackings, and other gruesome acts of mayhem do have their value in changing the dynamics of an otherwise intractable political conflict between forces of unequal power.
Terrorists are created because a situation they find intolerable persists without recourse. Terrorism as a tactic it is practiced because it can and does often work.
Brecher, Gary. Torture & Truth . The Exile ( Moscow , Russia ). < 21 Nov. 2004.
Divishi, Schlomo. The Role of Intelligence in Modern Warfare. New York : Buxton Press. 2002.
Fromkin,David. The Strategy of Terrorism. Foreign Affairs, July 1975.
Lenin, V.I. Where to Begin?  Collected Writings.1903. < November 17, 2004 .
US Navy War College Assessment Study.Strategies and Policies of Terrorism. 2002