The four horsemen are symbolic. They are also the same as the first four Seals of the Seven Seals. All these things are symbols of events or sets of events; they are not literal. The first four Seals are also called four horsemen to show that they occur at the same time.

[Revelation 6]
{6:1} And I saw that the Lamb had opened one of the seven seals. And I heard one of the four living creatures saying, in a voice like thunder: “Draw near and see.”
{6:2} And I saw, and behold, a white horse. And he who was sitting upon it was holding a bow, and a crown was given to him, and he went forth conquering, so that he might prevail.

This event is World War 3, the war of the Muslim extremists, led by Iran and Iraq (ISIS). They will use at least two nuclear weapons. I said “at least”. They will attack the U.S., conquer Europe, and win the War.

The first horseman is not Jesus. The conquering is not the Church spreading the Gospel. Rather, the Muslim extremists have great success conquering a vast territory; they persecute Christians and try to force Christians to convert to Islam.

{6:3} And when he had opened the second seal, I heard the second living creature saying: “Draw near and see.”
{6:4} And another horse went forth, which was red. And it was granted to him who was sitting upon it that he would take peace from the earth, and that they would kill one another. And a great sword was given to him.

At the same time, the 2020’s, there will be great civil unrest: violent crimes, violent protests, misuse of law enforcement and the military. Many persons will die as this will affect every nation. This is not a war, but civil unrest.

{6:5} And when he had opened the third seal, I heard the third living creature saying: “Draw near and see.” And behold, a black horse. And he who was sitting upon it was holding a balance in his hand.
{6:6} And I heard something like a voice in the midst of the four living creatures saying, “A double measure of wheat for a denarius, and three double measures of barley for a denarius, but do no harm to wine and oil.”
{6:7} And when he had opened the fourth seal, I heard the voice of the fourth living creature saying: “Draw near and see.”

The third event, occurring about the same time as the other events, is a great famine, which will be worse in the wealthy nations. Wine and oil represent luxury goods, which will be widely available, at the same time that food is scarce. At the time this was written, wheat was the food of the wealthy; barley the food of the poor. So one double-measure of wheat for a denarius (a days’ pay), but three for barley means the famine is worse in the wealthy nations; less severe in the developing nations.

{6:8} And behold, a pale horse. And he who was sitting upon it, his name was Death, and Hell was following him. And authority was given to him over the four parts of the earth, to destroy by the sword, by famine, and by death, and by the creatures of the earth.

Creatures of the earth includes virus and bacteria. This verse predicts multiple plagues of disease outbreaks. This suggests that during this period of time, something worse than Covid-19 occurs, maybe a later variant that is more deadly; maybe a completely different disease.

This fourth event is death from many different causes, and also the effect that the fear of death has on society.

When the War ends, then the other events subside, and there is a brief respite before the 5th Seal.