Jonathan Archer's decision in 2154 to take a warp coil by force from a stranded Illyrian vessel so that the crippled Enterprise could reach its meeting with Degra.
The theft of the Illyrian warp coil occurs in the Enterprise episode Damage. After the Battle of Azati Prime, Enterprise NX-01 is barely holding together and cannot go to warp, yet Archer has three days to reach a rendezvous with Degra that may stop the Xindi weapon.
The crew meet an Illyrian ship that has itself been damaged by the anomalies of the Expanse. Its captain trades some supplies but will not part with his warp coil, since without it his people face a journey home of three years.
Archer, against his own principles and T'Pol's objections, leads a boarding party and takes the coil, leaving trellium-D and food in exchange. The act weighs on him afterwards. The same episode reveals T'Pol's addiction to trellium.