Maintaining a retaliatory capacity great enough to prevent a first attack by a recognized enemy. Enough of the general capability of one's weapons and defences must be known by the enemy to prevent an attack. At the same time, the information must be minimal, to prevent the enemy from easily developing counter measures to the weapons. An ongoing commitment to the development and placement of weapons is necessary while various forms of negotiation take place.
The Cold War relied on deterrence, which took the form an arms race by well-matched superpowers, to provide a kind of stability to world order during the decades of the 1960s and '70s. Collapse of the Cold War in the 1980s, on the surface as a result of the collapse of the former USSR, was perhaps as much due to the unsustainable economic burden and limitation of options forced on both parties in maintaining the ever-escalating arms race.
Deterrence strategy requires a significant commitment to the cost of developing and maintaining weapons and defence systems.