THERE ARE TWO SEPARATE WARS DESCRIBED  IN THE SEVEN SEALS........

THE FIRST WAR :

THE GOG-MAGOG WAR  comes AT THE BEGINNING of the great  tribulation, and is described collectively in seals  #2, #3, & #4 . It is the Lord's "SHORTENED" tribulation judgment war exclusively UPON ISRAEL BEFORE the rapture which occurs in seal #6  BEFORE the great tribulation comes UPON THE WHOLE WORLD COMMENCING WHEN JESUS OPENS SEAL #7. The Gog-Magog War battleground is ON THE  MOUNTAINS OF ISRAEL, and God leaves ONE SIXTH  ( 1/6 ) of the Gog-Magog army as survivors according to :

Ezekiel 39:2-4

"And I will turn you back ( O' Gog ) , AND LEAVE BUT A SIXTH PART ( 1/6 ) OF YOU , and will cause you to come up FROM THE NORTH PARTS  , and  I WILL  BRING YOU UPON THE MOUNTAINS OF ISRAEL........YOU SHALL FALL UPON THE MOUNTAINS OF ISRAEL , you and all thy bands  , and the people that is with you....."

'THE SECOND WAR:

THE BATTLE OF ARMAGEDDON  comes AT THE END of the great tribulation UPON THE WHOLE WORLD, and is described in seal #7 in BOTH the 6th angel's trumpet judgment, and the 7th angel's trumpet judgment events according to :

Revelation  16:14 & 16 ( 6th angel )

"For they are the spirits of devils , working miracles , which go forth unto the kings of the earth  , AND OF THE WHOLE WORLD , to gather them together TO THE BATTLE OF THAT GREAT DAY OF GOD ALMIGHTY ......And He gathered them together into a place called, in the Hebrew tongue, ARMAGEDDON ." 

Revelation 16:17-21 ( 7th angel )

" And the 7th angel poured out his vial ............."

Revelation 19:19 & 21

"And I saw THE BEAST, and THE KINGS OF THE EARTH and THEIR ARMIES gathered together TO MAKE WAR AGAINST HIM (Jesus ) that sat on the white horse , and AGAINST HIS ARMY.........And THE  REMNANT WERE SLAIN  with the sword of Him that sat upon the white horse , which proceeds out of His  mouth."

SO, THERE YOU HAVE IT :........LOOK AT THE FOLLOWING DIFFERENCES :

The Gog -Magog  War is against ONLY the Nation of Israel and is carried out by a few armies FROM THE NORTH of Israel.

The Battle of  Armageddon is against ONLY the Lord Jesus Christ,  at His Second Coming,  by all the armies FROM THE WHOLE WORLD.

The Gog-Magog War's battlefield is  "UPON THE MOUNTAINS OF ISRAEL" where God brings them.

The Battle of Armageddon's battlefield is "IN A PLACE CALLED ARMAGEDDON" where God "gathers them together". 

The Gog-Magog Armies has A ONE SIXTH ( 1/6 ) SURVIVAL RATE  who are "turned back."

The Battle of Armageddon Armies HAVE  NO SURVIVORS . Even "THE REMNANT WERE SLAIN"  with the Lord's sword which proceeds out of His mouth ." 

The BEAST , who is the anti-Christ,  IS THE LEADER the armies  FROM the WHOLE WORLD who make war AGAINST THE LORD at the Battle of Armageddon.

GOG IS THE LEADER of the armies , "FROM THE  NORTH PARTS" , who make war exclusively AGAINST THE NATION OF ISRAEL.  

According to Your Holy Word,  come  Lord Jesus  !