Continuity mistake: Houston leans on the table while he makes his offer to Crockett at the party, but is standing completely straight just before he walks away. (00:05:40)
Continuity mistake: When Houston and Bowie are drinking in the street at night, Houston skips from looking directly at Bowie to suddenly gazing into space between shots as he says, "Texas, wasted on the Texans." (00:13:00)
Continuity mistake: When Travis leaves his son with the Ayerses, as he is turning to ride away, the man next to him mounts his horse in an instant. (00:15:20)
Continuity mistake: After he divulges his illness, Bowie is hunched over when he unsheathes his knife, but he is sitting up straight when he offers it to Crockett. (00:42:10)
Continuity mistake: In the shot where Travis hands Seguin the third message to Houston the off-center seal is closer to Travis. As Seguin takes it the seal is closer to him. (00:56:15)
Continuity mistake: Crockett leads a handful of soldiers out to burn down the shacks around the Alamo. In the first shot a few soldiers are speeding up to walk past Crockett, and in the next someone has already passed him. (01:02:20)
Continuity mistake: While one of his advisors tells Houston that some of the men from Gonzales have deserted to go to the Alamo, the advisor's hands change from clasped in front of him to on his knees. (01:06:55)
Continuity mistake: Immediately after Santa Ana allows civilians to leave the Alamo, Crockett tells Travis to talk to the men. Travis switches between shots from having his hands raised cleaning his gun to lowered out of the frame. (01:19:50)
Continuity mistake: When Santa Ana is planning the assault with his generals, the tip of the map pointer switches from light to dark constantly. (01:32:55)
Continuity mistake: While planning the assault, one of Santa Ana's generals objects to attacking before the cannon arrive. He unclasps his hands twice. (01:33:40)
Answer: Yes, the battle of San Jacinto really did last 18 minutes. Houston's army surprised the Mexican army while they were taking an afternoon nap.