Before the Iraq War when co-workers asked me whether I thought the Iraqis would fight, I said 90% of the army would not fight; half the Republican Guards would fight; and that I didn't know if the Special Republican Guards were fierce loyalists willing to fight to the last man or were pampered loyalists suitable only for killing unarmed civilians. They were the latter, as it turns out.
But that was just an impression. So I do think we need to be better in our models in portraying that factor. I don't know if Napoleon was right that the morale factor exceeds physical factors by a ratio of 3:1, but I do know that expensive equipment is just potential battlefield wreckage if the troops using them are poorly trained and lack the will to fight.
But I have doubts about how good we can really get. Certainly, ranges of will to fight should be modeled to show us the possibilities.
And then there is the problem of determining how will to fight changes. As I wrote over two decades ago about the Iran-Iraq War:
On January 8, 1987, Karbala Five signaled its beginning when waves of Iranians rushed the Iraqi lines northwest of Khorramshahr. As Rafsanjani predicted, the Iraqis stood their ground and fought. Final victory was not, however, the result. In standing to fight, the Iraqis gunned down the Iranians who stubbornly attacked in the face of crippling losses as they slowly shoved the Iraqis back. By January 22, 1987, the Iranians had advanced to within ten kilometers of Basra, the objective on which Iran pinned her hopes of victory. By the fourth week of the offensive, Iran's attack force was spent and the Iranians dug in to hold their exposed positions at the outskirts of Basra. Iraq's counter-attack called upon all the available reserves and smashed the Iranians to end the offensive for good. Perhaps 20,000 Iranians died in the battle. Iraq's casualties were about half of Iran's. Iraq's performance is notable in that Iraq withstood and won the kind of brutal bloodletting that supposedly only Iran could endure. Observers at the time saw only that Iran had launched yet another in a seemingly endless series of big offensives. They speculated about how many more of these attacks Iraq could endure. Actually, Iran broke at Karbala Five. It would be many months before observers began to wonder what was wrong with Iran when no further attacks were begun, yet it was true that the "Islamic Revolution bled to death in Karbala V." ...
While Iran continued to insist that ultimately it would be infantry who would decide the war, Iran had already let the usual season pass without launching a major offensive. This failure began to raise questions about what Iran was doing. One answer came in April 1988 when, after fewer than two days of fighting, Iraq recaptured the Fao peninsula with Operation Ramadan. Iraqi regular troops and Republican Guard forces backed by 2,000 tanks and 600 heavy guns plowed south and struck from the Gulf with a supporting amphibious assault. The Iranians were overwhelmed and showed no spirit of resistance. While it is true that the Iraqis outnumbered the Iranians by 8 to 1 odds, the contrast is amazing between April 1988 and February 1986, when Iranians fought hammer and tong for every square inch of worthless swamp on that peninsula. The day that Iranian infantry could not exact a heavy price for the terrain on which they stood was the day that Iran lost the war. April 18, 1988 was that day. [emphasis added]
Iranian will to fight and willingness to die had been the equalizer against Iraq's well-equipped conventional military relying on firepower and even poison gas to hold off more numerous Iranian light infantry backed by a smaller conventional Iranian force. But in January 1987, Iranian morale took a fatal hit. And in April 1988, it became apparent.
Yet when Iraqi forces eventually pushed into Iran to test the waters, Iranian morale rebounded. Iraq did not push their luck and agreed to end the fighting in August 1988.
What model can account for such changes in morale?
I'm not against the effort to improve our simulations by adding will to fight. Simulations without it are fairly worthless unless the material advantages are so great that no morale factor could affect the outcome. But if you have that, you hardly need a simulation to predict it.