First, a definition: attrition warfare is basically when one side, with greater resources and personnel, seeks to win a war by gradually wearing down an opposing force by sheer volume. It takes a while, and the result is massive loss of life and equipment, but because the one side has more of this to lose than the other side, the weaker side falls first.
This definition belies the kind of horrible hell that attrition warfare creates. A system where a side sacrifices life and expense in hopes that the other side will literally run out of the same resources first. Even though there is in fact a "winner" in this type of war, it's hard to argue that both sides aren't losers. Often the victor will find themselves completely depleted as well, in a situation where thousands or millions die in order to secure a victory in which the other side has simply run out of people to kill or resources to support them.
WWI, the War Between the States, and Angry Birds
World War One is a classic example of attrition warfare. The book All Quiet on the Western Front illustrates the horrors of this system: two forces entrenched without advance on either side, with the sole goal of killing each other until one side is gone.
Another great example is the Civil War, in which General Ulysses Grant exercised a similar policy in order to deplete the South of resources and lives. Because the North had more of both, they were able to win a war even while losing more lives. For instance, the siege of Petersburg, one of the last major battles of the war, saw the North lose 50,000 soldiers, of a force of nearly 125,000, while the South lost 32,000 of nearly 70,000 soldiers. The final casualty counts for the war: about 625,000 dead, about 412,200 wounded. Out of total forces of about 3,000,000. When one third of the forces of a war are killed or wounded, it doesn't represent a good situation.
Unless, of course, you're a team of birds seeking to get your eggs back or a tribe of green pigs trying to secure breakfast. In this scenario, self-sacrifice is worth it, as the goal, saving your children from being eaten or ensuring an end to the hunger of your countryswine, is more important than loss of your own life. And when you look at the way that these angry birds fight their war, it seems insane, scary, and unparalleled in history.
There seems to be an unending supply of resources on both sides of the war. Each level brings more pigs and more birds to the battlefield. And since the birds have weapons (exploding eggs, the ability to explode themselves, to speed up, etc.) and the pigs have strong forts, the losses on both sides are immense. Such a war can only be described as a war of attrition.
In the first battlefield, "Poached Eggs," alone, ninety-one birds face off against sixty-six pigs. Since the only goal is total destruction of pigs, all the birds can die and still accomplish a "victory." And early on, it seems they must do so, because as this hellish war progresses, the body counts rise, yet the size of the bird army decreases in comparison to the pig reserves.
Luckily for the birds, the pigs continually hide in fundamentally unsound structures, clumped together, and often near stores of dynamite. This strategy is inexplicable, but the pigs make up for it with sheer numbers. Total body count of the Angry Birds war (the original Angry Birds, not including Seasons or other spinoffs) thus far? 1176 birds, 1944 pigs dead. All over three eggs.
The pigs seem to have an unending force, and though the birds' forces are smaller, they are clearly more equipped for battle. In the battle of The Big Setup (areas 9-11), there are over twice as many pig losses as birds: 265 pigs to the much smaller 130 birds. Is this war worth it? I don't seek to pass judgment, but the losses on both sides make continuation of this conflict both insane and inevitable. As each side loses more and more soldiers, the sunk cost of this war becomes too much to bear. Maybe the pigs will cut their massive losses and surrender the eggs, or maybe the birds will realize that three children are not worth the loss of thousands of birds of a feather, but no matter what happens, in the war of Angry Birds, there can be no winner. Both sides have already lost, long, long ago.
[Data I harvested from the game: Angry Birds Casualties]