Field marshal, general of the army, and similar titles are the highest rank in Army service; they are rarely granted in industrialized countries other than during major wars. The rank is sometimes self-awarded by dictators of small countries. Some countries use the simple marshal, which also can be a civil or ceremonial rank. It may have a suffix such as Marshal of the Soviet Union.
The term generalissimo is sometimes used to designate the commander-in-chief of a national military; the implication is that such a person exercises direct command and control, rather than being civilian head of government.
There can be naval and air equivalents, such as Admiral of the Fleet/Fleet Admiral or Marshal of the Royal Air Force/General of the Air Force.