Jesus was not talking about Heaven heaven. He was talking about the first heaven. The atmosphere of the Earth. The bible talks about three heavens. First is the atmoshpere of Earth Second is (I think) space. The stars etc. Third is Heaven heaven. Our home.
The war in the heavens is in our own sphere.
what I can make out so far from that verse is that from the days of John the Baptist.. until now.
from John the Baptist until when Jesus is talking could only be one year time.
so Jesus was talking about around 1978 years ago
lasting for only a year, so this must be studied in that way.
I can only speculate that what Jesus meant is that violent people try to take kingdom of heaven by force without God's gift of Jesus and grace. but want it for themselves freely without repentance nor love and belief in God and His Messiah.
Genesis 1:1 In the beginning God created the heaven (the stars and planets, the skies) and the earth. Genesis 1:8
And God called the firmament (this expanse) Heaven. ...
The atmosphere Genesis 1:20 And God said, Let the waters bring forth abundantly the moving creature that hath life, and fowl that may fly above the earth in the open firmament of heaven.
Heaven heaven (lol how would you describe it? Ok. Home)
2 Corinthians 12:2 I knew a man in Christ above fourteen years ago, (whether in the body, I cannot tell; or whether out of the body, I cannot tell: God knoweth such an one caught up to the third heaven.