The Imps had Tom Hamer sent off after just three minutes and Conor McGrandles followed him off the pitch 20 minutes later, with Konstantinos Mavropanos heading West Ham ahead on the stroke of half time.
The second half was dominated by West Ham, with further goals coming from Edvin Austbo, Jarrod Bowen, Pablo and a Tomas Soucek brace, as the Imps manfully tried to keep the score down.
In their first league encounter for nearly 70 years, Lincoln made five changes from the 3-0 defeat to Sheffield United, with Hamer and Callum Elder making their first league starts for several weeks, while the West Ham side saw four new faces from their 1-1 draw with QPR.
Brace bagged: Tomas Soucek
PA
Disaster struck for Lincoln with the game in its infancy, when the recalled Hamer – starting his first game since August 22 – was shown a straight red card by referee Andrew Kitchen after he lunged recklessly at Joel Veltman leaving the Hammers right-back in a heap on the floor.
City kept their composure in the face of adversity, though, more than matching their opponents as the half continued.
West Ham nearly took the lead in the 22nd minute when Bowen’s corner was headed into the ground and wide by Mohamadou Kante.
City were then reduced to nine men a minute later when McGrandles shanked a pass back to keeper George Wickens from just inside his own half and as Bowen ran on to the wayward ball, the chasing Scot had no option but to grab a piece of the frontman’s shirt and haul him to the ground 40 yards from goal, and being the last man, the inevitable red card was produced from Kitchen’s top pocket.
City then had the next attack, with Ben House slicing a shot high and wide, with Mavropanos firing well over at the other end.
West Ham began to control proceedings and they struck just before the break, finally breaking City’s brave resistance when Bowen’s corner was headed in from close range by Mavropanos.
Goalscorer: Jarrod Bowen
PA
It took the Hammers just three minutes of the second half to double their lead when half-time substitute Austbo curled a powerful effort into the top corner from just inside the City box.
Bowen made it 3-0 a minute later, scuffing a left-footed shot that somehow trickled into the Imps net past an unsighted Wickens.
A Max Kilman volley flashed just wide for the visitors, before Pablo then made it 4-0 to West Ham, finishing off an Austbo pass.
Austbo brought another save out of Wickens and then sub Soucek added a fifth, lifting a shot over Wickens after 78 minutes.
Soucek made it six a minute from time, following up to slow home after Wickens had parried a Piroe shot.