If you think this happens only on the company you work for, surprise surprise, this "war" appears in many software developer companies as I happen to discovered in a dev exchange session during a Magento Meetup.
So, what's the problem? It seems to be that the developers claim that the sales guys are selling too much, and sales shrug their shoulders and keep on selling because that's what they do.
For a start let's say for a fact that sometimes developers are way up to the eyes and can't handle either the amount of work they have or the delivery dates people up in the chain of command are expecting them to accomplish. I'm not whining about it, I'm saying it happens to me in several occasions and it's something companies acknowledge by time to time (therefore, a fact).
If you are a developer going through this, then of course you are going to complain when a new project arrives as "you simply don't have more time to do it and nobody seems to understand that".
Time passes and you, developer, contain your discomfort deep inside, only having as a escape pipe your rolling-eyes attitude when a new client is presented. That means that when you encourage yourself to talk about this problem, with the sales team, is already late: you're angry, the sales team is angry too because they know by talk around the water cooler that the developers are complaining, so the discussion is getting to nowhere.
Sorry to disappoint you, my fellow developer, but to keep the company open for business the sales guys must attract new clients. Sales gotta sales, and, on top of that, the company must remain competitive, which means that the estimates provided in the commercial proposals must be competitives.
Stand in the shoes of a client picking a company for his next project: you will look at the estimates written in the proposal from the different companies you're consulting before choosing one, in addition to take into consideration the quality their provide.
Finally, the sales team times are different than the ones experienced by the developers team. Pre sales can take months, so it's hard to predict right now how busy the developers are going to be in, let's say, 10 months from now.
If you put your dev problems aside for a second, the explanations coming from the sales team are understandable, so give the sales guys a break.
I can see that both sides are right but unwilling to listen to the other. Nobody talks to nobody, developers raise complaint among developers only, sales within sales, and the real problem is never faced.
Up to this point we must agree that developers happens to have too much on their plate, and sales must keep on selling because everything I just said, but nobody is going to quit doing what they're doing to solve "the problems from the other side", at least nobody is going to do just that literally.
Understand that it's not about your problems and their problems, but a problem we have as a whole team.
The first step toward a solution is to start seeing this as an integrated team between devs and sales, no separate teams. Otherwise, if you can't accomplish this, then become a freelance and sell your time by the hour, because whether you are a developer or sales you're only thinking about yourself and not seeing the big picture, missing an opportunity to be a better company and benefiting you, plus everybody in the process.
Start talking, and planning together, but don't wait until you're mad. And find common ground about the problems you are facing, because sometimes it's not about changing the reality you're living but more about facing it and accepting it. Everybody, devs and sales, acknowledging the same reality (the same reality being the key words in this sentence).
Not changing the reality but just accepting it? Here's an idea...
Wouldn't be better to work in a place where a salesperson sells "the impossible", but closes the door behind the client, turns to the developers and says "Look, this project's delivery dates are challenging, but it's a key client we had to win"? Wouldn't be better to work in a place where, after that, the developers team says "Okay, we both agree on the times for this new client to be very difficult, but since we both agree on that let's work this out internally"?
Resolve it indoors! Keep on selling, good job, then sit on the same table and plan altogether with the developers team how are you going to accomplish the deadlines. It's impossible to get it done in one month? What if two devs work on this instead of one as it was originally planned? Wait, does this augmented reality requirement must be on the go live or can it be postponed for the support phase? Work it out as a team!
When I say that it's not about changing the reality but accepting it I'm saying that as long as we agreed on the problem, as long as we stand on the same boat knowing what's going on inside the company, both devs and sales, there's an opportunity to fix what's going on.
And, if not, if you don't think this means fixing anything... at least you'll be working on a place where the "enemy" is not inside the same building, causing the working environment to be much better, less stressful for sure.