What does the second Seal and the red horse represent?
The second seal reveals a red horse whose rider is given power to take peace from the earth, causing war and mutual slaughter, and he is armed with a great sword; this rider is identified as an angel who oversees matters of war and peace on the earth.
When the Lamb opens the second seal, John hears the call "Come and see," and a red horse goes forth. Revelation 6:3-4 records it plainly: "And when he had opened the second seal, I heard the second beast say, Come and see. And there went out another horse that was red: and power was given to him that sat thereon to take peace from the earth, and that they should kill one another: and there was given unto him a great sword." The rider of this horse is an angel, one of the real spiritual entities described as "the four spirits of the heavens" who stand in the presence of the Lord of all the earth and patrol to and fro through it.
The red horse rider is granted authority to remove peace from among the nations, resulting in violence, war, and mutual killing. The great sword given to him signifies the scope of destruction he is empowered to bring. He is not a symbol of some earthly nation or force, but a real heavenly agent assigned specifically to oversee matters of war and peace on the earth, able either to strip peace away or permit it to remain according to God's will.
Zechariah's vision helps clarify who this rider is and what he does. In Zechariah 1:8-11, a man riding a red horse stands among the myrtle trees with other horses behind him, and these are identified as those the Lord has sent to walk to and fro through the earth. When they report that "all the earth sitteth still, and is at rest," it shows that global peace had been allowed to persist, even among nations that had cruelly afflicted God's people and had not yet been brought to account. This troubled the red horse rider, since he carries a burden for justice regarding the nations, not because he desires chaos, but because peace was resting on those who deserved judgment.
Within the structure of the seals, the second seal does not itself cause war to break out at that moment. Rather, it foreshadows a major theme running through the rest of the book: war and violence as one of the defining forces at work in the last days. The opening of this seal informs the reader that the red horse rider is one of the agents whose influence will be seen again and again once the book itself is opened, preparing believers to recognize war and bloodshed as a recurring feature of the events yet to unfold.
The scriptures
And when he had opened the second seal, I heard the second beast say, Come and see. And there went out another horse that was red: and power was given to him that sat thereon to take peace from the earth, and that they should kill one another: and there was given unto him a great sword.
I saw by night, and behold a man riding upon a red horse, and he stood among the myrtle trees that were in the bottom; and behind him were there red horses, speckled, and white. Then said I, O my lord, what are these? And the angel that talked with me said unto me, I will shew thee what these be. And the man that stood among the myrtle trees answered and said, These are they whom the LORD hath sent to walk to and fro through the earth. And they answered the angel of the LORD that stood among the myrtle trees, and said, We have walked to and fro through the earth, and, behold, all the earth sitteth still, and is at rest.
And the angel answered and said unto me, These are the four spirits of the heavens, which go forth from standing before the LORD of all the earth.
From the books
This answer is drawn from these passages in the Mary Banks Faith Library.