In Act 1, Scene 4, the First Murderer uses a simile to mock and ironize the Duke of Clarence’s faith in Richard’s kindness. Clarence believes that Richard cares for him, but the Murderer knows otherwise:
O, do not slander him, for he is kind.
Right, as snow in harvest.
Come, you deceive yourself.
The First Murderer's response employs a simile, comparing Richard's alleged kindness to snow during a harvest. Snow at harvest time would be disastrous for crops, as it would make them wither and freeze. This is the murderer’s way of saying that Richard’s "kindness" is both deadly and non-existent. It’s also a roundabout way of saying that Richard being kind would be impossible or wildly unlikely, just as “snow in harvest” would be.
Shakespeare is also using situational irony in this moment. Clarence is blindly defending Richard’s kindness. He can’t fathom that it is precisely Richard’s malevolence that has brought the Murderers to his door. The audience, privy to Richard’s plotting, perceives the grave danger Clarence is in. Where they might expect Clarence to be suspicious of his younger brother’s actions, the Duke remains steadfast in his belief in Richard’s goodness. This ironic simile serves to highlight how naïve Clarence is, and to show how effective Richard’s plotting and manipulations have been.
It’s also interesting to note here that history has revealed George, Duke of Clarence, to have been a traitor himself. He switched sides many times in the battles between York and Lancaster, and was eventually sentenced to die for treason against his older brother, Edward VI. It’s rumored that—instead of the conventional beheading—he asked to be drowned in a barrel of malmsey, a sweet wine.
Just before the Battle of Bosworth Field comes a powerful scene where Richard experiences a prophetic nightmare. The words he utters when he wakes are both situationally ironic and dense with foreshadowing:
Richard starteth up out of a dream.
RICHARD: Give me another horse! Bind up my wounds! Have mercy, Jesu!—
This plea is dripping with situational irony. Richard, a character notorious for his ruthlessness and disregard for human life, now finds himself pleading for mercy. Throughout the play, Richard has been a character defined by his lack of compassion. His cold and calculating demeanor, coupled with his merciless acts of violence, paints him as a man devoid of empathy. Yet, in this moment, the tables are turned. Richard’s own desperation and helplessness mirror the very emotions of those he tormented. It is ironic that he, who showed no mercy, seeks it so fervently now. His plea is also religious in nature, invoking Jesus for help. As Richard’s actions comprise many "mortal sins"—acts for which one would be damned without sincere repentance and restitution—crying out for Jesus at this point seems pathetically pointless. He defied all religious morals and disregarded all cries for mercy directed toward him, but he reaches for divine comfort when he's afraid.
The scene also explicitly foreshadows what is coming for Richard at Bosworth Field. His plea for a horse and for his wounds to be bound is immediately mirrored in the battlefield scene that follows this nightmare. The play makes use of several moments of supernatural warning, so Richard dreaming of his own death doesn’t seem all that unusual. However, his unraveling is indicative of the fall that is to come. His cry for mercy, from human or divine sources, remains unheeded, much like the cries of those he wronged. This call for "mercy, Jesu!" sets the stage for the approaching poetic justice of Richard's defeat and death.
In Act 5, Scene 4 of Richard III, a wet and miserable scene unfolds that’s packed with situational irony. Richard—a character who throughout the play is depicted as cunning, ruthless, and power-hungry—finds himself in a dire situation on the battlefield. On foot and vulnerable in the mud, he cries out:
A horse! a horse! my kingdom for a horse!
The gravity of the situation is profound, which makes the irony it contains seem even more acute. Richard schemed, betrayed, and murdered in his quest for the throne. His ambition knew no bounds, and his thirst for power was unquenchable. He would have, it seems, done anything to get and then retain his “kingdom.” However, he's losing a vital battle and is about to lose his kingdom. He’s in such a vulnerable state in this scene that he is now willing to trade that very kingdom for a horse in order to stay alive.
Richard’s cry illuminates how the tides have turned. His own life is now hanging by a thread. While it’s unlikely that he would have actually honored the trade if someone had offered him a horse, the fact that he’d make the offer illustrates the change in his fortunes. Without a horse, he’s very likely to die on the battlefield. On a horse, he’s somewhat protected and can move quickly. On the ground, he’s reduced to the position of a common soldier and has no means of escape.
A kingdom that he won through enormous effort and sacrifice could now be lost for lack of a horse. For a man whose life was dominated by the quest for a throne, the throne itself becomes insignificant in his hour of need. The situation is ironic, but it's also an example of Shakespeare’s brand of poetic justice. Richard, who would stop at nothing to win the crown, is about to die because he’s on the ground instead of on horseback.