Offense Defense And The Causes Of War Homework

Offense-Defense Differentiation • The other major variable that affects how strongly the security dilemma operates is whether weapons and policies that protect the state also provide the capability for attack. • If the offense has the advantage, conquest and aggression will still be possible. • States will have to worry that even if the other’s military posture shows that it is peaceful now, it will develop aggressive intentions in the future. • The differentiation between defense and offense allows status-quo states to behave in ways different from aggressors. o Status-quo states can identify each other, laying foundation for cooperation o Status-quo states will obtain advance warning when others plan aggression and can plan counter-attack measures. o If all states support the status quo, an obvious arms control agreement is a ban on weapons useful for attacking. • Problems: Even when differentiation is possible, a status-quo power will want offensive arms under 3 conditions: o If the offense has too great an advantage over the defense, protection through defensive forces will be too expensive. o Status-quo states may need offensive weapons to regain territory lost in the opening stages of war. o The state may feel that it must be prepared to take the offensive either because the other side will make peace only if it loses territory or because the state has commitments to attack if the other makes war on a 3 rd party. • Aggressors as well as status quo powers require defensive forces as a prelude to obtaining offensive forces. • Whether a weapon is offensive or defensive depends on the particular situation • If total immobility clearly defines a system that is defensive only, limited mobility is ambiguous. • Any forces that for various reasons fight well only when on their own soil in effect lack mobility and are therefore defensive • Weapons that are particularly effective in reducing fortifications and barriers are of great value to the offense. • Weapons and strategies that depend for their effectiveness on surprise are almost always offensive. • It is not always possible to distinguish between forces that are most effective for holding territory and forces optimally designed for taking it. When such a distinction is possible, the central characteristic of the security dilemma is removed and most of the troublesome consequences of anarchy is removed. Offense-Defense Differentiation and Strategic Nuclear Weapons • In the context of deterrence, offensive weapons are those that provide defense. • There are 4 worlds derived from combinations of 1) the advantage of offense/defense and whether 2) their postures can be distinguished. •


Van Evera provides ten self-reinforcing effects when offensive dominates to argue that war is more likely when conquest of a state is easy. He produced a number of factors that would lead states to have offensive positions, namely: Military, geographical, socio-political, and diplomatic. In the final section, he sought to relate his hypotheses to case studies of Europe since 1789s, ancient China during Spring, Autumn and Warring states era, and the United States since 1789.


War is far more likely when conquest is easy.

Ten War Causing Effects, when offensive dominates:

  1. A: Opportunistic expansion – Ease of taking over/conquering encourages predatory tendencies of other states – even by temperate powers.
    1. Cost less to attempt and succeeds more often
    2. Lower fear of reprisal because of quick and clean victory
  2. B:Self-defense is more difficult; hence states are less secure and it drives them to pursue defensive expansion
    1. When offense capabilities is relatively greater than defense, borders are less defensible, and the state would seek to improve defense by coveting other’s territory and resources.
    2. Conversely, states with more defensible borders are more accepting of status quo.
  3. C: Build up in military by one state, through expansion or in military power, creates increased insecurity and threatens national security for others. As such it prompts a more violent response to resist expansionism.
    1. When conquest is easy, resources becomes easily cumulated, creating more violent response because each resource gained tips the balance between hegemonic dominance and demise of a state.
    2. Expectation of one another’s conduct as neighbouring states are made aggressive by temptation and fear of expansion
  4. D: First-strike advantages are larger, raising dangers of preemptive war.
    1. Surprise attacks has the incentive of requiring a lower force-ratio, and yield greater reward for less casualty.
  5. E: Windows of opportunity and vulnerability are larger, raising dangers of preventive war.
    1. Since when conquest is easy countries are more persuaded to go to wage preemptive wars, a shift in force-ratio causes great hope and alarm to others.
    2. This makes any event that changes the resource balance one that can potentially lead to war.
  6. F: States more often adopt fait accompli (meaning: a thing that has already happened or been decided before those affected hear about it, leaving them with no option but to accept it) diplomatic tactics, and such tactics more often trigger war
    1. Relations between states deteriorates further when states proceed with disingenuous engagement, while aiming for political victory and uphold national pride. This increases changes of war
    2. Common when offense is greater.
  7. G:State negotiate less readily and cooperatively;hence negotiations fail more often, and disputes fester unresolved.
    1. When there is less faith in upholding agreements (due to past behaviour), hard bargaining  that causes deadlocks, and compliance is difficult to verify.
  8. H: States enshroud foreign and defense policy in tighter secrecy, raising the risk of miscalculation and diplomatic blunder.
    1. Advantage in withholding information
    2. Underestimating ease of conquest can encourage others to pursue aggression
  9. I: Arms racing is faster and harder to control, raising the risk of preventive wars and wars of false optimism
    1. Offense dominance intensifies arms racing.
    2. Vicious cycle as stated above
  10. J: Offense dominance is self-feeding (self-reinforcing). As conquest grows easier, state adopt policies (E.g. more offensive military doctrines) that make conquest still easier. This magnifies effects 1-9.
    1. States buy more offesive forces when offense dominates, as they prefer more successful type of force, so they buy defensive forces when the defense is strong and offensive forces when the offense is strong
    2. Alliances assume ore offensive character when offense dominates as aggressors can drag allies into war, and insecure states cannot afford to see their allies defeated.
    3. Collective attack by alliance overwhelms state’s defenses.

Conclusion: Offense dominance position is hard to escape and leads to a downward spiral, and its the same effect for when offense is weak but others perceive it to be strong.

Causes of Offense and Defense Dominance:

  1. Military Factors
    1. Military Technology – changes ease of acquiring/improving capacity for offense or defense
      1. Defense technologies: fortifications, lethal small arms, bardbed wire, and trenches, railroad, nuclear
      2. Offense technologies: mass infantry weapons, lethal small arms
    2. Doctrine
      1. Offense: Blitzkrieg and Armoured technology
    3. Strategy
      1. Military posture and deployment
      2. Wartime operations – aggresive operations corrode key enemy defenses
  2. Geography
    1. Natural Barriers – hinder logistics and support routes
    2. Man-made Barriers – urban sprawl can slow down movement of armour
    3. Size of buffer zone
  3. Social and Political Order
    1. Popularity of state – Popular states can raise large and more loyal armies, granted passage through other states, able to organise citizens for guerrilla resistance
  4. Diplomatic Factors
    1. Type of Diplomatic arrangements that strengthen defense:
      1. Collective security systems – promise of mutual aid against aggression by any system member.
      2. Defensive alliances – promise of mutual aid against outside aggressor
      3. Balancing behaviour by neutral states – selective participation in conflict by neutral states, to balance against the stronger side.

Tests of Offense-Defense Theory

Predictions types: 1) Prime, and 2) Explanatory

Prime Predictions:

  1. War more common in periods when conquest is easy or believed to be easy
  2. States that believe they have high offensive or defensive vulnerability will initiate fights with other states
  3. A state will initiate and fight more wars in periods when it has, or thinks that it has, larger offensive opportunities and defensive capabilities.

Cases studies

  1. Europe since 1789 – Supports prime predictions 1 and 2
  2. China – Supports prime prediction 1
  3. USA – Supports prime predictions 2 and 3

Explanatory Predictions:

  1. Phenomena A-J will be more abundant in eras of real or perceived offense dominance: the ten phenomena should increase as offense strengthens and diminsh as offense weakens
  2. States that have or  believe they have large offensive opportunities or defensive vulnerabilities will more strongly embrace policies that embody phenomena A-J.

Case Studies:

  1. Europe: Supports explanatory predictions 1 and 2, by illustrating A-B, and offers some evidence for C-J
  2. USA: Supports explanatory prediction 2.


  1. Offense-defense theory is a good theory
    1. Large importance – posited cause has large effects
    2. Wide-explanatory range – across different domains and covers different phenomenas
    3. Wide real-world applicability
  2. Large Prescirptive utility
  3. Satisfying – explained by its roots in 10 war causing effects

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