White doesn't need to defend his pawn just yet. His pressure on the e-file and black's uncastled king will aid white in recovering his pawn if black plays Nxe4.
4... a6
?! Black thinks this is a Morphy's defense? This allows the basic removal of the guard tactic. Here black doesn't have the Qd4 resource as white's e-pawn is adequately defended. Better was 4...Bc5 or Nxe4
5. Bb5xc6
! Removal of the e-pawn's defender.
5... dxc6
Better than bxc6
6. Nf3xe5
Ah... nothing like a free pawn especially a centre pawn.
6... Bf8d6
?! Not too good. Black tries to develop with tempo but this invites a fork. Better was 6...Be7 or Bc5.
7. Ne5f3
The best move. 7.d4 is also possible, but the text gives black more problems. A fork is threatened i.e. 8.d4
7... Bc8g4
?? Black pins the knight supporting the e-pawn push. Now if 8.e5 Bxe5 9.Nxe5 Bxd1 and white is lost. But as we shall see, 7...Be7 was mandatory.
8. e5
! White plays 8.e5 anyway! Remember folks, whenever a king is on an open file, tactics are possible.