A.T. Robertson Commentary Revelation 19:11

"And I saw the heaven opened; and behold, a white horse, and he that sat thereon called Faithful and True; and in righteous he doth judge and make war." — Revelation 19:11 (ASV)

The heaven opened (τον ουρανον ηνεωιγμενον). Perfect passive participle (triple reduplication) of ανοιγω. Accusative case after ειδον. So Ezekiel (1:1) begins his prophecy. See also the baptism of Jesus (Matthew 3:16; Luke 3:21, but σχιζομενους in Mr 1:10). Jesus predicted the opened heavens to Nathanael (John 1:51). In Re 4:1 a door is opened in heaven, the sanctuary is opened (11:19; 15:5), angels come out of heaven (10:1; 14:17; 18:1), and sounds come from heaven (19:1).

Behold, a white horse (ιδου ιππος λευκος). Nominative case because of ιδου, not ειδον. Cf. 6:2 for ιππος λευκος. The emblem of victory in both cases, but the riders are very different. Here it is the Messiah who is the Warrior, as is made plain by "Faithful and True" (πιστος κα αληθινος), epithets already applied to Christ (1:5; 3:7,14). Cf. also 22:6.

In righteousness he doth judge and make war (εν δικαιοσυνη κρινε κα πολεμε). See Isa 11:3f.. The Messiah is both Judge and Warrior, but he does both in righteousness (15:3; 16:5,7; 19:2). He passes judgment on the beast (antichrist) and makes war on him. Satan had offered Christ a victory of compromise which was rejected.