There are many similarities between Rev. 6:12-17 and Ezek.38:19-20. Do you think the Magog was could start at the opening of the 6th Seal? And, something must have happened for the fourth horsemen to kill 1/4 of the earth’s population. Could it be a war mentioned in the Bible? It seems strange that it wouldnt be elaborated on for that level of causalities.
I believe the Battle of Ezekiel precedes the beginning of Daniel’s 70th week, which precedes all the seal judgments. The 70th week can’t begin until Israel officially recognizes God’s involvement in their affairs, which happens in Ezekiel 39:22 at the end of Ezekiel’s battle. The effect of the seal judgments could either involve 1/4th of the Earth’s area or 1/4th of its population. While I lean toward the population, no one is sure which. But in either case, the only information about it comes from the earlier introduction of the red horseman (number 2) who has power to take peace from the Earth (Rev. 6:4). This brings war, which results in famine (number 3), and death (number 4).