There are three important considerations that nations must take into account when a nation makes a decision of whether or not to release biological weapons on an enemy. The first, and most complex, question would be the morality of the issue. Is the situation such that releasing the weapon would contradict the values of the attacking nation? US President Harry Truman struggled with this conflict before deciding to use nuclear weapons on Japan to end World War II. In the end a nation must decide if it can live with the judgement history passes upon it for using a weapon of mass destruction and if its use was justified by the situation.
The next factor to consider would be the nation's ability to control or contain the weapon once released. The weapon could wipe out the nation's enemy, but could it be contained? Would it damage neighboring nations or even possibly come back to haunt the attacking nation itself? How would their own troops be safeguarded from the weapon? These questions must be answered definitively before making the decision to use biological weapons.
Lastly, the international political ramifications of the action must be weighed by the nation considering use of a biological weapon. In 1972 over one hundred nations signed a treaty banning the use or stockpile of biological weapons. What would the fallout from using these weapons be? Even if the nation did not sign the treat, it has to consider what actions other nations would take in response to the attack.