The obvious answer is, it can't, but my contention is that it should. Certainly not always, not even often, but assuming the weaker player does most everything right and the stronger one does not, it should at least be possible.  

I would welcome anything that makes this game more challenging and gets us away from the patent solution of winning all battles by throwing more troops and money at a problem. The varying defensive values for troops is one such welcome exception as it at least allows us to marginally affect battle outcomes by making the effort of thinking about it, but IMO there aren't many other similar examples. So here goes: 

Suggestions impossible to implement: 

• Troop formations - if one looks at historic battles, especially in the pre-industrial ages, formations, weather and terrain choices were integral to battle outcomes, allowing outnumbered troops to hold their own. 
  
  
• A bit more "fog of war" in regard to long-range raids. It would be so interesting if longer range raids weren't identified from 10h away but rather from 15 or 30 min. (or some such value). The fact that it is simpler to move a city rather than to launch a long distance raid with any chance at success is IMO a good sign that there's something wrong here … unless Greeks lived in trailer parks. 
  
  
• A bit less "fog of war" regarding Emporia, Caps, Pans and protectorates. Why is it impossible to know the first thing about a city one has sieged, from the amount of resources available to possible incoming raids, is beyond me. One can't even scout one's own protectorates to see what's what (I know, in itself counterintuitive, but IMO still better than what it is now). 
  
  
• Seasons … perhaps in a monthly rotation, reducing or increasing unit speed, augmenting or detracting from unit strengths, perhaps even dependent on the unit types.  
  

I am well aware that none of these suggestions will be implemented, not only would they entail massive changes in game mechanics (and probably make it simpler to build a new game :-) but also discourage more casual players, but perhaps … 

… someone has a suggestion that would make this game a bit more challenging without having to throw out the dev with the bathwater ;-). 

Yes, I'm aware of unit XPs (available on FB and eagerly awaited on .com servers) but, like the general, the use of enhancers, city upgrades and Phylarch bonuses, it mostly always comes down to strength beats smarts. Every time. 

Cheers 
P. 

PS: The reason I am not posting this to the "Suggestions" thread is that they would not be accepted (and understandably so), but perhaps someone out there has a suggestion that would be both sensible AND practical … "Hope is that thing with feathers ..."