Until meeting Remus, Alexander was able to tour the camp freely without any distractions since most of the men had not had the time to even register his arrival.
But it took only a few moments with Remus to make the man have all that peace of mind get destroyed.
What Remus basically was suggesting was that since the enemy planned to flood them with undrinkable seawater, then all they would have to do is use heat to boil the waste salt out, thus leaving them with only pure drinkable water.
And viola, with this single simple move, they would be able to foil the enemy's plan.
Remus got the idea after remembering how Alexander made salt back in Zanzan, using exactly this method.
The only difference was there he used coal as fuel, whereas here the young general proposed to use all the wood and timber in the mansion as kindling.
Remus was personally quite pleased with being able to come up with a 'simple yet ingenious' plan.