The idea of using weapons to achieve equilibrium between powers and maintain peace is not novel, but its effectiveness depends on the technological balance between competing powers.
One of the accepted theories of the Cold War era was that if both sides had ballistic nuclear missiles, than neither side would risk a first strike. The theory was called Mutually Assured Destruction or MAD, and it meant that both sides would lose the war due to the virtually guaranteed destruction of all parties in a hypothetical nuclear conflict.
This theory may work when both actors in the scenario are rational and accept that death is a final and negative outcome. But it may not add any level of security if one or more of those actors are not rational, have have an apocalyptic view of the world that honors death before life.
The other limitation is when one side is able to neutralize the ballistic missiles to an effective degree of the other side, unbalancing the relationship between the powers and giving incentives for instigating increasingly aggressive actions.
Theories like MAD may be challenged by new anti-aircraft technologies able to successfully target and hit smaller and faster weapons like cruise missiles and even incoming ballistic missiles. The Reagan administration announced a program to develop laser weapons that could destroy Soviet missiles while in space. The Soviet response was to create missiles with multiple warheads so that there was a greater chance of some of the warheads reaching their targets after encountering countermeasures.
While this “Star Wars” technology was not likely to succeed in the 1980s, current anti-aircraft systems may be a solution to advanced ballistic missile threats coming from actors who have challenges being rational in their behavior.
While the early Patriot Missile systems had claimed success against SCUD missiles coming from Iraq in the 1991 Gulf War, the reality was that few were successful. But the idea that they could protect their bases and allies tamped down the likelihood that the entire conflict would escalate.
The use of the Iron Dome missile system follows this line of rationale. The new technology reduces the need for a harsh response where innocent civilians are in danger as the effects of ballistic missiles are muted by Iron Dome, eliminating a full scale response to aggressive gestures from both rational and non-rational actors.
The recent deployment of THAAD missiles to protect the region from North Korean missile threats is an another example. However, in this scenario China perceives this deployment as an aggressive gesture itself close to their own territory.
Generally, anti-aircraft missiles do not perform the function of a surface-to-surface missile without major reformatting, and even in that case, the warhead on a surface-to-air missile would not cause any major damage due to its smaller size and the design of how SAM missiles combusts.
The THAAD system therefore is not a direct threat to China as a means to launch an assault on Chinese territory, but it could target and shoot down Chinese aircraft and maybe even their ballistic capabilities.
Anti-aircraft missiles on opposing sides of a conflict act as two shields, whereas ballistic missiles are only used as an offensive weapon a conflict. Thus, it could be argued that they are most effective as a political tool to diffuse a conflict, without making aggressive gestures like placing missiles in Cuba during the Cold War.
Conflicts could occur if both sides have equivalent missile shields, but one side has a large ballistic missile advantage over the other that might still cause a great deal of damage. In either case, rational actors would hopefully see Mutually Assured Defense as a valuable step back from Mutually Assured Destruction, and take steps to reduce the ability for non-rational actions to have a sword when selling or giving them a very capable shield.