Assalam Alaikum,
There are two main, what can be called, Aqa'id (or creeds) in fighting. There is the Western (Aqeedah) of fighting, and then there is the Eastern. The most basic, basic "Fundamental" to the Western (Aqeedah) of fighting is (Basically):
"More firing (meaning weapons that fire rapidly) less men"
and the most basic, basic "Fundamental" of the Eastern (Aqeedah) of fighting is (basically):
"More men less shooting"
Each fundamental as it's reasons and defects, I will not mention all of them for I want to keep it short. I can basically say that the Western Aqeedah of fighting wastes fire power, while the eastern one wastes souls. And the Islamic Aqeedah of fighting is (medium path) between these, it neither wastes fire power and weapons, nor does it waste the souls of the Muslims, and in Fact the leader should lead the army with caution, and try to keep the men safe, and not use them for example as sacrifice to get to a goal.
So that was just a glimpse at the Islamic Aqeedah for fighting, as well as it is far superior over all other ways and Aqa'id of fighting. But sadly, we can see that it is rare if even possible to see one army of a so called "Islamic/Muslim country" following this Islamic Aqeedah, rather they are following the Western or eastern Aqa'id of fighting, or they are following a mix of these two.
I find it fair enough to mention, that the Islamic Aqeedah of fighting is part of Islam, and because of this Aqeedah of fighting the early Muslims were so successful in battle. So this Aqidah has already been proven to work so well, but now we Muslims are missing that Aqeedah, and the application of it in our Armies today. For that reason it's existence needs to be renewed, as well as the Islamic Army. Once renewed, Jihad would also be renewed, and not be used by some Muslims who commit suicide bombings, or go off by them selves to do what they call Jihad, ignoring the Fact that there should be order, a leader, weapons, men, and strategy and so many other things.
I end by mentioning an Authentic Hadith narrated in Saheeh Muslim:
[quote]من مات ولم يغزُ، ولم يحدث نفسه بالغزو، مات على شعبة من النفاق
The Messenger of Allah (sallallahu 'alaihi wa sallam) said, "He who dies without having fought in the Cause of Allah or without having thought of doing so, will die with one characteristic of hypocrisy in him."[/quote]
http://sunnah.com/riyadussaliheen/12#57