Faith in Jesus teaches that no earthly war is 'good'. For He said: All who take up the sword will die by the sword.
It is true that the Old Testament contains wars, but Christ introduced a radical New Covenant of love for one's enemies (Matthew 5:38-44). When He told Peter to put his sword away in Gethsemane, He was stopping a seemingly 'justified' act of defense, showing that His Kingdom is not of this world (John 18:36).
Furthermore, we must be discerning regarding end-times prophecies. Scripture warns of a deceptive, surface-level peace and prosperity for Israel, often associated with a covenant that involves the figure of the Antichrist (Daniel 9:27). Therefore, supporting earthly wars today can be spiritually risky if they align with man-made agendas rather than divine will.
According to the Bible, the only 'just' war in the end times is the one led by Christ Himself, who will destroy the Lawless One and his allies with the breath of His mouth at His coming (2 Thessalonians 2:8, Revelation 19:11-21). Until then, our call as followers of Jesus is to reflect the Prince of Peace, not to rely on the swords of men.