This is the question ask by a teen - David; when he went to the line to supply his brothers[1Sam.17:29]. The Hebrew warriors had squared off for battle; and were being tormented, out front by The Champion - Goliath. The Anointing of our Creator was on David; and the Lord had much to demonstrate.
Goliath was a result of Fallen-angles[Nephilim, Gen.6] mating with women. This repeated itself, because the giants are hybrids. The flood of Noah's day wiped out many of them. Here David would face one; and God through David would show the brothers how to do it: Goliath also had four brothers.
The mighty-warrior-Joshua encountered Christ Jesus[Josh.5:13-15] geared up for battle, and ask "Art thou for us or for our adversaries"? One should make double-sure that we, are on Christ Jesus side: and stop getting this twisted. Fake-leaders[Hypocrites] must convince the popularity that war is just-and God is on our side: not so!
The Champion came up and was talking big-trash; he by his god, cursed the God of the Hebrews. This professional-warrior was heavily geared-up and trained from his youth for this vocation. David was a voluntary worshipper, and a skilled sheep-herder, that was anointed to lead, and protect. Carnal weapons, against Spiritual weapons!
The professional from Gath, quickly lost his head: that is the way our Lord handles His business. Man prolongs and make merchandise of people and war. King Saul offered up his own gear that was rejected for something that had been proven.
Nothing righteous has changed. "What is the cause"? Insure that the Righteous side has been identified - and get on it!