WARWICK You forget That we are those which chased you from the field And slew your fathers, and with colors spread, Marched through the city to the palace gates. (1.1.92-95)
Warwick tells Henry and company that they've already lost to York and his army, and they'd better watch their backs. Here, "colors" means the battle flags that Henry's army was carrying... and had to run away with after York's army chased them off the battlefield. Warwick is basically saying, "Hey, there's no point fighting anymore, but we can keep going if you want York to beat you again."
KING HENRY No. First shall war unpeople this my realm; Ay, and their colors, often borne in France, And now in England to our heart's great sorrow, Shall be my winding-sheet. (1.1.130-133)
At the beginning, Henry thinks this war will be his "winding-sheet," which is another word for a burial shroud. If this isn't foreshadowing, we don't know what is. Henry can already see that the war will bring about his end, in one way or another. There's also something scary about the image of war "unpeopling" Henry's land. What's the point of even having a kingdom if everyone who lives there has been killed off in a war?
RICHARD Therefore, to arms! And, father, do but think How sweet a thing it is to wear a crown, […] I cannot rest Until the white rose that I wear by dyed Even in the lukewarm blood of Henry's heart. (1.2.28-29, 32-24)
When Richard is trying to convince York to fight Henry, he uses this description of war. It's poetic, it's symbolic, and it's downright gross. But hey, it does get across the fact that Richard is out for blood if someone stands between his dad and the crown. He's always willing to fight for his crown—er, his family's crown—er, actually, with Richard, it's never totally clear. For more on the white rose, head on over to "Symbolism, Imagery, Allegory."
YORK The army of the queen hath got the field. My uncles both are slain in rescuing me; And all my followers to the eager foe Turn back and fly like ships before the wind, Or lambs pursued by hunger-starvèd wolves. (1.4.1-5)
Poor York. He knows he will lose this battle to Margaret and her army. He also knows that his uncles died to save him, and his sons are still out there fighting. The animalistic imagery he uses here (for example, wolves) points out how barbaric the war has become. The men are a bunch of animals now, ripping each other apart.
KING HENRY O piteous spectacle! O bloody times! Whiles lions war and battle for their dens, Poor harmless lambs abide their enmity. Weep, wretched man. I'll aid thee tear for tear... (1.5.73-76)
Looking at father and son killing each other, Henry gets depressed. He realizes that this is what the war has done to his country (not to mention to his family). It seems like no one besides Henry realizes that this is what's going on. Henry realizes that war isn't a game or a popularity contest; it's thousands of people killing each other.
GEORGE Yet know thou, since we have begun to strike, We'll never leave till we have hewn thee down, Or bathed thy growing with our heated bloods. (2.2.171-173)
George threatens Margaret with war after she, with Clifford's help, has killed York and Rutland. It looks like war brings on more war; it's a never-ending cycle because, as George points out, everyone is hot-blooded (angry) over what the other side has done. An eye for an eye leaves the whole world blind?
KING HENRY This battle fares like to the morning's war, When dying clouds contend with growing light, What time the shepherd, blowing of his nails, Can neither call it perfect day nor night. (2.5.1-4)
What a pretty image for such a nasty action. Henry's beautiful metaphor for war (daybreak fighting off the night) shows how far removed he is from it. He has the luxury of sitting on a hill, watching the whole thing from a distance. We never see Henry fight for his crown. He leaves that to his wife, child, and army. On the other hand, though, most of the characters in the play act as if war isn't all that big of a deal; they think it's totally legit to go to battle over what is essentially a family squabble. It's only later that some of them see how nasty the whole thing can be.
EDWARD See who it is: and, now the battle's ended, If friend or foe, let him be gently used. (2.6.43-44)
Edward and posse hear someone die, and Edward tells his comrades that they should treat this guy like a gentleman even if he is an enemy. Edward's remark shows that there is still some honor in war... or so it seems. Edward wants to leave this man to die with his dignity, but that quickly goes out the window when they all see it's Clifford who is dying. Since Clifford killed Rutland, they don't care about him one bit. So much for honor, after all.
QUEEN MARGARET What's worse than murderer, that I may name it? No, no, my heart will burst an if I speak, And I will speak, that so my heart may burst. Butchers and villains, bloody cannibals... (5.5.58-61)
Once her son is killed, Margaret speaks out against all the stuff that's been going down. The thing is—she's right. These people are butchers, carelessly throwing away human life. Um... then again, so is she. This is the woman who chopped off York's head after taunting him with the blood of his dead son, right? We'd say that puts a little kink in her soapbox speech. The point, though, may be that Margaret isn't able to fully understand the horrible consequences of her actions until it her son is killed in front of her; that's when things really hit home.
EDWARD Once more we sit in England's royal throne, Repurchased with the blood of enemies. What valiant foemen, like to autumn's corn, Have we mowed down in tops of all their pride! (5.7.1-4)
At the end of the war, Edward promises peace. He reminds us of a weird paradox: that peace is only brought about with war. Well, that's what he says, anyway; we're not totally sure if that has to be true. Is this just something Edward is telling himself so that he can sleep at night?