In what threatened to be a feisty affair after both sides were reduced to 14 men inside the opening 12 minutes, Armagh ended Louth's unbeaten run in spectacular style as they cruised to victory in Drogheda to blow the promotion race wide open.
The men from the Orchard County got off to the worst possible start when Aidan Forker was shown red in the opening minute but they regrouped well and raced into a 1-1 to 0-0 lead with Ciaran McKeever finding the back of the net in the 10th minute.
Two minutes later referee Ciaran Branagan had the red card out once again as he sent off Louth's Anthony Williams for an off-the-ball incident. Pauric Smith finally got Louth up and running with a fine point after 12 minutes but a Niall Rowland goal two minutes later left them in big trouble.
A Ryan Burns free right on the stroke of half time left the scoreboard reading 2-5 to 0-6 in favour of Armagh at the break.
Louth needed a quick start to the second half to get back into it but it was Kieran McGeeney's men who stretched their lead with ace marksman Jamie Clarke scoring 1-3, including a goal from a penalty, in the space of five minutes to put the game to bed.
Louth now face a trip to Tipperary to re-ignite their promotion bid.
SCORERS - Armagh: J Clarke 1-3; N Rowland 1-1; R Grugan 0-4 (2fs); N Grimley 0-4 (2fs); C McKeever 1-0; P Hughes; S Sheridan; G McParland 0-1 each. Louth: R Burns 0-4 (3fs, 145); P Smith 0-3; T Durnin 0-2; G McSorley; C McKeever 0-1 each.
ARMAGH - B Hughes 7; P Hughes 8, C Vernon 7, G McCabe 8; A McKay 7, B Donaghy 7, N Rowland 8; A Findon 7, S Sheridan 7; N Grimley 8, A Duffy 7, R Grugan 8; A Forker6, C McKeever 7, J Clarke 8. Subs: B Crealy 6 for A Findon, J Morgan 7 for G McCabe, C O'Hanlon 6 for A Duffy, N McConville 6 for R Grugan, S Heffron 6 for N Rowland.
LOUTH - C Lynch 6; K Carr 5, P Reilly 5, P Rath 5; A Williams 6, J Bingham 5, D Maguire 5; D Byrne 5, T Durnin 7; B Duffy 5, P Smith 6, J Stewart 5; R Burns 7 , E O'Connor 5, R Moore 5. Subs: A Reid 5 for R Moore, C McKeever 5 for E O'Connor, K Murphy 5 for K Carr, R Holcroft N/A for R Burns.
Ref - C Branagan (Down).