The object of giving medals, stars and ribbons is to give pride and pleasure to those who have deserved them. At the same time a distinction is something which everybody does not possess. If all have it, it is of less value. There must, therefore, be heart-burnings and disappointments on the borderline. A medal glitters, but it also casts a shadow. The task of drawing up regulations for such awards is one which does not admit of a perfect solution. It is not possible to satisfy everybody without running the risk of satisfying nobody. All that is possible is to give the greatest satisfaction to the greatest number and to hurt the feelings of the fewest.
Winston Churchill (Prime Minister) – 22 March 1944
Which leads to the following from JSP 761:
0803. The decision to institute a new United Kingdom award – a separate campaign medal or the OSM – does not depend on any formal declaration of hostilities but is based largely upon evidence of the degree of danger to life and limb and the rigours of terrain, climate, etc...
and
The main factors that should be considered in the overall criteria for a proposal in any particular operational situation are:
a. The risk and danger to life.
b. The style and force of the enemy, adversary or opponent.
c. The physical and mental stress and rigours that had to be experienced by individuals; and, indeed, the numbers of individuals and/or units involved or committed to the operation.
d. The extent to which climate, weather and terrain factors affected the operational situation.
e. The restrictions, limitations and difficulty in implementing the operation.
f. The time (stated in number of days) and the number of air sorties (which may have a limit on how many on any one day) that should count towards eligibility.
g. The geographical boundaries within which eligibility will count (this does not have to accord with the officially defined operational area).