21st Century Revelation's premise is that we are living in the End Times right before the Tribulation. Zechariah 1 and 6 describe four horses at rest during Babylonian captivity. The key to the horses is to understand the colors of the end time powers. A world map shows four horses as end time regional powers on the run before the Tribulation.

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 there were red horses, speckled, and white. Then said I, O my lord, what are these? These are they whom the LORD has sent to walk to and fro through the earth. ... all the earth sits still, and is at rest (Zechariah 1:8-9, 10-11).

Revelation 4-5 describes the throne of our sovereign God and Creator of the universe. In His right hand is a scroll with seven seals, the title deed to earth. Who is worth to open the scroll? No angel or mere human was found worthy. Then John saw the Lion from the tribe of Judah as the Lamb of God. Because of His perfect sacrifice on the cross, Jesus Christ is worthy to inherit the earth.

They sung a new song, saying, Thou are worthy to take the book, and to open the seals: for thou were slain, and has redeemed us to God by thy blood out of every kindred, tongue, people and nation (Revelation 5:9).

Revelation 6 and 8 describe seven seals. Four are called "Four Horses of the Apocalypse." To understand the horses, focus on color and start with red.
.
Seal 2 - Red Horse of War (Revelation 6:3-4) One definition of red is communism/socialism. In 862, Russia was established and by 1462, Ivan the Great starts the expansion. In 1848, Karl Marx wrote Communist Manifesto. Russia went red in 1917 and China in 1949, running loose during World War I, World War II and the Cold War. After hibernating, the Russian bear is back to its old Soviet ways (Daniel 7:5). The woman (religion) sits on a red beast (government) Revelation 17:3.
.
Seal 3 - Black Horse of Trade (Revelation 6:5-6) In accounting, the opposite of red is black, the opposite of communism is capitalism. No famine but people live paycheck to paycheck. Wheat and barley are bought with a day's wage (Matthew 20:1-2). The first British king ruled in 824 and by 1588, the British defeat the Spanish Armada and control a quarter of earth. In 1890, the United States eagle became the economic superpower. The eagle and pair of scales are on the dollar.
.
Seal 4 - Green Horse of Death (Revelation 6:7-8) Bible translators have difficulty with chloros. Like communism and capitalism, this is a major world view. Chloros is translated green, the color of Islam. In 610, Mohammed founded Islam that spread to Spain by 711 and today controls a quarter of the world's population (~2 billion). The green horse fought the black horse during the Barbary Pirates, World War I, Iran Hostage Crisis, Iraq Wars, Al-Qaeda and the Islamic State.
.
Seal 1 - White Horse of Conquest (Revelation 6:1-2) Islam is false religion while the white horse is apostasy within the Catholic and Protestant churches. In 313 AD, Constantine proclaimed religious toleration in the Roman Empire. By 380, Christianity was the official religion as church and state merge. The white horse was on the run during the Crusades and Spanish Inquisition but lost ground to other horses during the last few hundred years. The pope leads ~1.4 billion Catholics. The False Prophet combines apostasy and false religion into the 2nd Beast of world religion (Revelation 13:11-12).

Look at a world map to see the horses on the run today. The red horse of communism rules China and Russia. The black horse of capitalism rules Australia, Canada, India, United States and Far East Asia. The green horse of Islam rules Middle East, North Africa and Southeast Asia. The white horse of apostasy rules Central Africa and Latin America. The European Union was more Catholic/capitalist but trending toward socialist/Islam. All wars are political, religious or economic conflicts.

The Horses of the Apocalypse are on the run today (Matthew 24:5-6, 7-8). The four horses of Revelation 6 are fighting but later unite. At the beginning of his reign, Antichrist merges communism, capitalism, Islam and apostasy to rule the one-world Beast (political, religious, economic systems).

Four seals are fulfilled but three seals are future.

Seal 5 - Martyrs (Revelation 6:9-10, 11) Martyrs faithful to God have been around since Cain murdered Abel. The martyrs in Revelation 6 are Saints redeemed during the Tribulation and wait impatiently for God to bring justice. They are given white robes and are told to rest for a while. God's primary goal is to redeem the world but a secondary goal is to bring judgment against those who reject His Son and persecute His people.
.
Seals 6 & 7 - Great Tribulation (Revelation 6:12-13, 14-15, 16-17, 8:1, 3-4, 5) The final two seals occur at the end of World War IV (Russia) (Ezekiel 38:19, 21-22) and World War V (Armageddon). The 7th seal, trumpet, bowl end with lighting, thunder, great hail, earthquakes as mountains and island move at the Second Coming.

The book of Revelation is not sequential but a spiral of parallel events that have shorter time spans until the return of Jesus Christ. Seals begin at the merger of church and Roman state. Seals, trumpets, Tribulation, Antichrist, bowls, Mystery Babylon and Armageddon end at the Second Coming.

Since we are over one hundred years into the Laodicean period of the Church Age, we can see horses on the run and trumpet sounding before seven years of Tribulation begins. Wake up Laodicean church!

References: 21st Century Revelation: World Wars, Iraq Wars & End Wars - Chapter 20: Players in the Game, Chapter 21: Four Horses on the Run, Revelation Outline, Covenant, Tribulation, Revelation, 21st Century View, Daniel, America, Timeline of the Tribulation, Chronology of Man, Hebcal, Endtime Ministries