Steinbeck uses this intercalary chapter to continue his attack on commercial farming methods and their utter disregard for human decency. His sympathy for an agrarian lifestyle is characterized by his angry description of the ploy of larger companies to buy canneries and then underbid, and eventually destroy, the small farmer.
The perceived threat of the Okies to the California natives is examined once again as the result of basic decencies denied to a large number of people by a powerful few. The desperation among the hordes of displaced workers has grown to such a level that even the store clerks know they must fight to protect their own small holdings.
Both Chapters 21 and 25 make use of a biblically influenced prose style that resonates with angry admonishes and wrath. By maintaining an extended allusion to Julia Ward Howe's "The Battle Hymn of the Republic," which Steinbeck had planned at one time to have printed somewhere in the novel, these two chapters create a mood of apocalyptic reckoning. The context of the book's title in the song refers to the Book of Revelation (Rev. 14:19), "The angel swung his sickle on the earth, gathered its grapes and threw them into the great winepress of the God's wrath." Steinbeck's wife actually chose the title for the novel, although the author was pleased with the choice because he valued its American emphasis and believed it would offset both fascist and communist criticisms or identities, according to biographer, Jackson Benson. The first four lines of the song are, "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 lightening of his terrible swift sword, / His truth is marching on." Steinbeck describes the armies of bitterness marching in Chapter 9 and ends this chapter with a warning that the anger of the migrant workers is beginning to "ferment." He continues these allusions in Chapter 25.
