God fights. Here's His fight plan.

Why is a battle hymn necessary?  Because God fights.
Where is the proof that God fights? The birth of two countries, Israel and America.
What are some battle hymns and where are they found?  How about the book of Psalms, and the Battle Hymn of the Republic for starters…. and then there are the "banners," the flags, the motivating truths...

"You have shown Your people hard things;
You have made us drink the wine of confusion.
You have given a banner to those who fear You,
That it may be displayed because of the truth."  Psalm 60:3-4

PUTTING BANNERS into PERSPECTIVE:
About "Banners" like, "Don't Tread on Me" - "Don't Tread on Me" is not in the Bible. We the people, serve the one and only KING. It's more like, "Don't Tread on HE"……. People have become more, "ME" and "SELFIE" aware, (yes a selfie, pun). What is happening to seeking God first?  "Seek first the kingdom of God" Matthew 6:33

PUTTING THE BATTLE into PERSPECTIVE:
Potential Americans once sought freedom from English monarchy and won it by hard fought war. Some might say America's Revolutionary War was led by another King, King Jesus Christ. Many Americans are Christian Soldiers, who seek to follow and serve God through every war, serving to set the captives free, fight tyranny and help build freedom for the oppressed.  I think American soldiers have a special place in God's heart.
"One man of you shall chase a thousand, for the LORD your God is He who fights for you, as He promised you. Therefore take careful heed to yourselves, that you love the LORD your God."
Joshua 23:10-11. It follows soldiers would want to sing a battle hymn. The Merriam-Webster dictionary definition of hymn is, "a song of praise." The Bible tells us to pray without ceasing and to raise praise.
A Battle Hymn is necessary because earth-life is fraught with many wars. There are fleshly, worldly, wars and crippling, wounding spiritual wars, thought wars and so on.  I often notice that our enemy Satan, usually fires shots first toward my spirit. God is my fortress, His word my wall and His praises are my prayer and power.  Then I see from my spirit, the enemy strategies becoming blazingly obvious and instantly defeatable, often by the power of one word,  JESUS.
I love this battle hymn from the 1860's:

THE BATTLE HYMN OF THE REPUBLIC - here are some of the words:

Mine eyes have seen the glory of the coming of the Lord;

He is trampling out the vintage where the grapes of wrath are stored;

He hath loosed the fateful lightning of His terrible swift sword:

His truth is marching on.

(Chorus)

Glory, glory, hallelujah!

Glory, glory, hallelujah!

Glory, glory, hallelujah!

His truth is marching on.

I have seen Him in the watch-fires of a hundred circling camps,

They have builded Him an altar in the evening dews and damps;

I can read His righteous sentence by the dim and flaring lamps:

His day is marching on.

PUTTING the FIGHT, into FORMED and INFORMED PRAYERS, READYING, FOR HIS ACTIONS.
God of all truth, Lover of our souls, Forgiver and Designer of Repentance, we ask YOU to form and inform our prayers. May our prayers splash into the ongoing flow of holy intercession constantly offered by our High Priest, Your Son, Our Matchless Jesus.  Earth is descending into so much evil, such godlessness, so much pain, torture and lack of justice anywhere. We seek You first. We seek never to pray amiss. We exist under the banner of Your love.  All of earth is yearning for a king, JESUS. All governments fail, falling into inevitable power struggles that seem to never end. You sent Your Son and we crucified Him, each of our sins nailing Him to that cross. He finished Your plan of redemption with His perfect, personal, supernatural power. He calls us the joy set before Him. Is it soon time, for the government to once and for all time, rest upon His shoulders? Help us spread the gospel with our responses, our leadings, our giftings, wherever You place us, be it sick in hospitals, healthy in the front lines or invisibly, home based tending to families. Help us spread the good news with our lives, our walks, our everything.  May all we do, point to You. Please deliver believers under fire, refugees in overcrowded camps, children being sent to America for safekeeping, elderly without funds or family to care for them, please intervene and cause us to come along side everyone's need as YOU equip and lead us. Help us hear Your directions and instructions of how to help, who to help and when to help. Give us Your wisdom and ears to hear.  Creation seems to be groaning. We call to YOU with thanks, praise and light to offer in Jesus' name.  We pray PEACE TO ISRAEL. Amen.

For many reasons, I no longer can think of America's Fourth of July celebrations without thinking of Israel. Happy Birthday America. We love you Israel and thank our God for you always.