Pergunta: Será que Joseph Smith dizer que ele seria um "segundo Muhammad," ameaçando espalhar suas crenças com a espada?
Question: Did Joseph Smith say that he would be a "second Muhammad," threatening to spread his beliefs with the sword?
The statement which Joseph is charged with making did not accord at all with how he had his followers behave
Some have argued that Joseph may have said something like this, but was doing so for rhetorical effect to frighten the Missourians into leaving the Saints alone. But, it is by no means certain that he said it at all. Some who made the claims returned to the Church, and other sources were motivated by hostility and a desire to portray the Saints as a military and religious threat.
This claim came from Thomas B. Marsh after he left the Church
The source of this claim is from Thomas B. Marsh, an apostate former president of the Quorum of the Twelve. In 1838, Marsh swore an affidavit in which he claimed to have heard Joseph Smith say:
he would yet tread down his enemies, and walk over their dead bodies; and if he was not let alone, he would be a second Mohammed to this generation, and that it would be one gore of blood from the Rocky Mountains to the Atlantic Ocean; that like Mohammed, whose motto in treating for peace was, 'the Alcoran or the Sword,' so should it be eventually with us, 'Joseph Smith or the Sword.' 
Green and Goldrup: "this threat was quite probably a mere fabrication by the disgruntled Marsh"
Arnold Green and Lawrence Goldrup noted in 1971 that "this threat was quite probably a mere fabrication by the disgruntled Marsh,"  and pointed out Orson Hyde (who was also disaffected at the time) later repented and returned, indicating that parts of the affidavit had been invented by Marsh. Marsh himself was later to repent and return to the Church, which casts further doubt on his story.
The tale was also repeated by George M. Hinkle, John Corrill, George Walter, and partially by Abner Scovil.  Joseph Smith's journal for the period notes:
some excitement was raised in the adjoining Counties, that is Ray & Clay, against us, in consequence of the suden departure of these wicked character[s], of the apostates from this Church, into that vicinity reporting false stories, and statements, but when they [the Missourians] come to hear the other side of the question their feeling[s] were all allayed upon that subject especially. 
It is, then, by no means certain that Joseph made this statement—the witnesses are all hostile, and clearly intended to frighten the Missourians
Joseph was under enormous pressure to defend the Saints against the repeated actions of mobbers. As historian Marvin Hill notes,
the actual response to belligerence when it occurred was much more restrained. Although the elders did confiscate property and burn houses, their attacks were generally aimed at specific enemies. Mormons had neither the inclination nor means to wage a general war of extermination against all mobbers, despite menacing talk. The only fatalities occurred in the skirmish with Bogart, where the elders got the worst of the fight. Had the prophet been intent on waging total war, it is unlikely he would have allowed Rigdon to issue his 4th of July warning, which only put the Missourians on guard. 
- History of The Church, 3:167 note. note BYU Studies link
- Arnold H. Green and Lawrence P. Goldrup, "Joseph Smith, An American Muhammad?: An Essay on the Perils of Historical Analogy," Dialogue: A Journal of Mormon Thought 6 no. 1, 46.
- David Grua, "From the Archives: Joseph Smith or the Sword!?," blog post at Juvenile Instructor blog (17 Nov 2007) off-site.
- JS, Journal, [July 1838], cited in Dean C. Jessee, ed., The Papers of Joseph Smith, vol. 2, Journal, 1832-1842 (Salt Lake City: Deseret Book Company, 1992), 255–256. ISBN 0875795455.; as cited in Juvenile Instructor, ibid.
- Marvin S. Hill, Quest for Refuge: The Mormon Flight from American Pluralism (Salt Lake City, UT: Signature Books, 1989), 97.