Education is one thing I would emphasize.  I would try to make sure that my soldiers understood what they were defending and understand the history of their country, their branch of the military, and their unit.  I would also make sure they also understood the principles of freedom and the importance of liberty.  When and if they go to war I want them to believe that are fighting for something, not just because they were told to.  This doesn't have to mean indoctrination and enduring long, boring lectures, but you could make it interesting and inspirational.  I would invite military veterans, historians, and political scientists to talk to the soldiers and encourage discussion. 

 

Realistic training is of course vital, but along with that I would try to instill within my soldiers a can-do attitude and a steadfast belief that they are the best would beat any other military force they would face.  I feel that this is one reason that the American military has been so successful.  A lot of Europeans sneer at the idea that American troops could possibly think that they are better than European troops, but the validity of the American sentiment is beside the point.  During most of the Cold War the US Army's whole military doctrine depended upon the US Army fighting vastly outnumbered in Central Europe.  I have talked to a number of soldiers that served in Germany in the 1980's, and they have described the troops that were serving in the Fulda Gap as extremely disciplined and confident.  Those men believed that they could stop the Russian hordes in their tracks, and many modern historians believe that they could have backed up that bravado had the balloon went up.  I'm not advocating tombstone courage or suicidal tactics, but I firmly believe that your troops need to believe in themselves and each other and believe that they will somehow get the job done when they need to. 

Build up and maintain a large reserve force, including stockpiled weapons and materials. 

 

Reserve forces can provide you with quickly available supplemental to fill out units that are not needed at full strength in peace time (like logistical units) and provide additional units (after a brief re-training period) so that regular units can be cycled out of combat for rest and rebuilding.

 Have a good supply of manpower from a lifestyle that imparts qualities translatable into warfare. Mountains for instance are practically mercenary factories. High tech equipment is easier to learn by those from high-tech countries. And so on.

This is very much a matter of chance. But if you are prepared to use mercs you can get some of the kind of people you want.

I've read somewhere that a happy childhood is beneficial to being a effective soldier later on. It makes it easier for the soldier to deal with the stress on the battlefield if I remember correctly.

 

Makes one wonder about parents abusing their children "to toughen them up".

Play lots of airsoft!!  (J/K!)

 

Giving NCO's more control over the training helps to, with more focus on squad based training rather than large manuevers.

1. Knowledge - as mentioned earlier know your nation it's ideals, and the values of their country

 

2. leadership, especially the NCO's units and armies that are top notch have top notch NCO's there is no single level of command than the NCO who lives with, trains and literally fathers their men.

 

Reserves supplies and such all the necessary, but the integrity of the small units within the army are far more important. In war adversity is the norm, and it is the NCO that is the key player in maintaining discipline and sense of purpose to each and every soldier.