Absent elaboration by Francis Scott Key prior to his death in 1843, some have speculated more recently about the meaning of phrases or verses, particularly the phrase "the hireling and slave" from the third stanza. According to British historian Robin Blackburn, the phrase allude to the thousands of ex-slaves in the British ranks organized as the Corps of Colonial Marines, who had been liberated by the British and demanded to be placed in the battle line "where they might expect to meet their former masters. " Mark Clague, a professor of musicology at the University of Michigan, argues that the "middle two verses of Key's lyric vilify the British enemy in the War of 1812" and "in no way glorifies or celebrates slavery. " Clague writes that "For Key . . . the British mercenaries were scoundrels and the Colonial Marines were traitors who threatened to spark a national insurrection. " This harshly anti-British nature of Verse 3 led to its omission in sheet music in World War I, when the British and the U. S. were allies. Responding to the assertion of writer Jon Schwarz of The Intercept that the song is a "celebration of slavery," Clague said that: "The reference to slaves is about the use and in some sense the manipulation, of black Americans to fight for the British, with the promise of freedom. The American forces included African-Americans as well as whites. The term 'freemen,' whose heroism is celebrated in the fourth stanza, would have encompassed both. "