First off, let's make clear what the Bible really said at Revelation 6, in which the King James Bible reads as "third beast" at verse 5, but accurately should read as "living creature", for the Greek word used there is zoon, meaning "a living thing", and not the Greek word therion meaning "a dangerous animal", as at Revelation 13:1.(Strong's Exhaustive Concordance of the Bible)
So, Revelation 6:5, 6 accurately reads: "When he opened the third seal, I heard the third living creature say: “Come !” And I saw, and look ! a black horse, and the one seated on it had a pair of scales in his hand. I heard what sounded like a voice in the midst of the four living creatures say: “A quart of wheat for a de·narʹi·us and three quarts of barley for a de·narʹi·us; and do not harm the olive oil and the wine."
But before Revelation 6:5, 6 can be understood, a person has to first grasp Revelation 6:1, 2, which starts "the ride of the four horsemen". And who is the rider on "the white horse" ? Revelation 19:11-14 identifies him as "the Word of God", with other riders on white horses (in which "white" in this context stands for righteous warfare) following him. And who is "the Word of God" ?
John 1:1, 14 helps to place who it is, as Jesus Christ, who is seen at Psalms 45, whereby it says: "Strap your sword on your side, O mighty one, in your dignity and your splendor. And in your splendor go on to victory; Ride in the cause of truth and humility and righteousness, and your right hand will accomplish awe-inspiring things. Your arrows are sharp, making peoples fall before you; They pierce the hearts of the king’s enemies."(Ps 45:3-5)
Thus, Revelation 6:1, 2 says: "And I saw when the Lamb opened one of the seven seals, and I heard one of the four living creatures (or angels) say with a voice like thunder: “Come !” And I saw, and look ! a white horse, and the one seated on it had a bow; and a crown was given him, and he went out conquering and to complete his conquest."
Here Jesus Christ is given a "crown", but to what ? What he had been waiting for thousands of years, that of receiving the kingship to the newly created heavenly government called God's Kingdom. At Luke 19, Jesus gave an illustration of "a man of noble birth (that) traveled to a distant land to secure kingly power for himself and return", that was about him taking hold of the reigns of the Kingdom, though it would be a long time coming in the 1st century before he received it.(Luke 19:12)
But to help a person grasp when Jesus was enthroned as king of God's Kingdom, Revelation 6:3, 4 says: "When he opened the second seal, I heard the second living creature say: “Come !” Another came out, a fiery-colored horse, and it was granted to the one seated on it to take peace away from the earth so that they should slaughter one another, and he was given a great sword."
What does the rider on the "fiery-colored horse" picture and when was it, ' granted........to take peace away from the earth so that they should slaughter one another, and he was given a great sword ' ? It pictures human warfare, and the year was 1914, when the first world war that involved almost the entire population of the earth, with some 93 percent being affected by it in some way.
This pinpoints the year when Jesus took the reigns of God's Kingdom as 1914. Now for the rider on the "black horse", in which its rider is holding a pair of scales, for carefully weighing out food in increments, for food shortage had now become real, whereby human warfare destroys the farmers, the farms and supply chains to the market for people, completely disrupting the availability of food, so that starvation sets in, for Revelation 6:5, 6 says: "When he opened the third seal, I heard the third living creature say: “Come !” And I saw, and look ! a black horse, and the one seated on it had a pair of scales in his hand. I heard what sounded like a voice in the midst of the four living creatures say: “A quart of wheat for a de·narʹi·us and three quarts of barley for a de·narʹi·us; and do not harm the olive oil and the wine", which only the rich could afford, due to sky-rocketing inflation.
One quart of wheat, which was considered as the best, cost the equal of a whole day's wage.(see Matt 20:2, in which workers was given one denarius per day) And barley was considered as not as good as wheat, so a person could buy three quarts of barley for a day's wage, but how far would this go with a large family ? Hunger would set in, for the pantries would be bare after only a short while, for just about all the money would have to go towards food, but then what about the other bills ? Something has to give.
Revelation 6:7, 8 now says: "When he opened the fourth seal, I heard the voice of the fourth living creature say: “Come !” And I saw, and look ! a pale horse, and the one seated on it had the name Death. And the Grave was closely following him. And authority was given them over the fourth part of the earth (or large number of people), to kill with a long sword (through warfare) and with food shortage and with deadly plague (such as the Spanish Flu of 1918-20, The Aisan Flu of 1958, the Hong Kong Flu of 1967, and now COVID-19) and by the wild beasts (or political governments) of the earth (that maim and kill, slaughtering any and everyone it wants to)."
The rider on a "pale horse" that can denote being sickly, leading to death, is seen. So, the last rider here means that with Jesus enthronement as king of God's Kingdom, whereby he takes his newly acquired power and goes forth "conquering", this starts a chain reaction of "woes" that will not relent until "the war of the great day of God the Almighty" called Armageddon, a world situation (and not a location in Israel) that pits "the kings of the earth and their armies" against God's heavenly Kingdom, so that they are "crushed" out of existence.(Dan 2:44; Rev 19:19-21)
When Jesus became king of God's Kingdom in 1914, he then set out to forcibly throw his archenemy, Satan the Devil, out of heaven, along with his demonic angels, who had free access to the heavens up to that point, this being the unseen war at Revelation 12:7-10.
When Satan was forced out of heaven, Revelation 12:12 says that "on this account be glad, you heavens and you who reside in them ! (who no longer has to put up with Satan's false accusations and lies) Woe for the earth and for the sea, because the Devil has come down to you, having great anger, knowing that he has a short period of time."
Satan, now very angry, goes and moves an already unstable situation in the Balkan States to start World War I, using a 19 year old Serbian terrorist named Gavrilo Princip to assassinate the Archduke Franz Ferdinand (and his wife Sophie) of Austria-Hungary on June 28, 1914, so that this starts "the kettle boiling" and by July 28, 1914, Austria-Hungary (after securing unconditional support of Germany) declares war on Serbia, and in which Germany declares war on Russia (which supported Serbia) for mobilizing its army.
By August 4, 1914, Britain and France had declared war on Germany, so that a European war (with the countries and their allies taking a firm stance, creating the Allied and Axis sides) had began, and by April 1917, the United States became involved, making it now a true World War, that when it ended on November 11, 1918, an estimated 20 million soldiers and civilians had lost their lives, this being the greatest war in human history up to this point, only to be eclipsed some 27 years later by World War II, whereby an estimated 60 + million lives were lost. Truly, a "great sword" was given to the rider on "the fiery colored horse", so that "Death and the Grave" reaped a "bountiful harvest" and will keep on riding until Armageddon, as we are seeing in the Russia-Ukraine war.