Also, let's pull Alan back from the Abbey. With Curbiston secure, it appears these incursions were merely bored beseigers raiding upriver past some nearsighted nitwits. He can escort the women that wish to return to their husbands and to help with the harvesting and threshing of the wheat, then he can ride to join us. He's itching for some action, I can palpably feel it. Marna can stay in the Abbey and rest, while perusing their excellent libraries.
Also, I'll gather up the military advice from before the new developments that still pertains now, and put it together in a more readable and actionable state for scouting southward.
Preparations
First, we gather our usual mounted retinue, bolstered by whatever recruits from the battle proved adequate with horses, and ride to Curbiston. This might be 68 men. Meanwhile we put Fin--if he wishes command--aboard our new Navy with a strong crew comprised mostly of good levy archers and a few halberdiers to repel boarders. This means we take about 60 men from among the peasant levies as crew.
Convince Denton and Percival to send their foot soldiers duly to Curbiston, but help us scout southward with their light cavalry while waiting for other lords to muster the remainder of this month. Scouting is a good excuse, and they are more apt to follow our lead than remain with Foles, whom they also dislike. Many of the other lords haven't been planning for this, so it will take them time to respond during such an important season. This means our land force will be about 115 armed mounted men, plus messengers and scouts.
Land Forces:
3 Knights, 3 squires -- including Alan!
Retinue: 35 halberdier dragoons, 23 archer and 10 ranger dragoons
Allies: 50 light cavalry
Naval Forces:
3 Longboats, 50 archer levies, 10 Halberd levies, stock of fire arrows, and towed fire rafts
Establishing a Base
Everything goes like before in a different direction. We can ask locals and refugees about where the enemy has been and travel faster through relatively safe areas. Find the farthest river-thown untouched by raiders, and make that place the base for our scouts and navy to coordinate our probing downstream. If none, then find a safe place to hide some supplies offloaded from the boat, and make this a rendezvous point. Ideally, it would be up a minor tributary river. Then we take our advance slower from there.
Open the Way
On land, scouts on fast horses go a few hours ahead of our main body to find where the enemy scouts are posted, and draw them into pursuit. These appear to aggressively have pursued our earlier messenger, so plan a good ambush along a roadside copse or hedgerow or abandoned village. We ambush them with our dismounted dragoons and our cavalry allies mop up. Then with better knowledge of the lands up ahead, the scouts can give us even closer ambush points to repeat this. We creep closer this way and open the land approaches to deeper scouting.
On sea, Finn sails downstream under enemy colors, and pinpoints the nearest enemy naval outpost on the river. He ought not to engage unless its smaller than three boats, but turn back and seek us out. Use his towed rafts, if pursued. We can coordinate another land-water assault like last time on any medium-sized outpost. We want to open the riverway to deeper scouting.
Scouting the Main Strength
Some well-planned ambushes will put the fear-of-god in their outriders that hunted down our earlier messenger so aggressively, and they'll become more passive to direct scouting of their main encampment. Then we get detailed information on them. We want force strengths and dispositions, where their baggage camp is, how it is supplied, whether they've build siege engines, and of course the status of the city itself.
I have hopes for also scouting their naval strength, and main landing sites, but feel that they are very strong in that aspect. Finn must first and above all seek to remain upstream of strong threats. Unless... someone else suggests going 100% undercover and "counting coup" among the enemy fleet disguised as a raider?
Also, if we should ever need to sail into the Duke's City in enemy longboats... Have the local sailmakers dye an entire sail with our heraldry and save it for later. No chance of friendly fire at all can be taken when you're actually in an enemy craft.
Special Note: Lastly, all of this is to be done in haste. It's a bit vexing that we sit around the first week or two of the month while Denton trotted off to the Count, when we did suggest that we all go in readiness. Our father-in-law is in dire peril! Even though nothing was really there, we could have swung south much faster.