I want to summarize what we know so far, so as to identify what would be the most fruitful places to pursue further. The bottom line right now is that:

1 - It may be that the unit that liberated Preuilly was an element of 5th Infantry Division, or it may have been a XX Corps non-divisional element. It was almost certainly not an element of 7th Armored Division element. If it was a XX Corps non-divisional element (other than 3rd Cavalry), then it is going to be difficult to find the unit, since these smaller units (e.g. Artillery Groups or rear echelon groups) do not usually have associations nor contacts who we can find on the internet. So the best hope for a quick answer is the 5th Infantry Division or someone very familiar with it.

2 - The passage of the forward elements of both 7th Armd Div and 5th Inf Div by Noon on 27 August to the north and to the south of Preuilly seems to indicate either that Preuilly was liberated early in the day by an advance recon unit (which fits with the photos of recon vehicles) or that the liberation of Preuilly was later in the day by a rear echelon unit. I do not recall if we have established what time of day Preuilly was liberated, but this would be useful to know.

3 - The maps help us rule out units but not to identify the liberators. So the photos may hold the key, either in the patches or in the markings on the vehicles.

What follows is the basis for my reaching these directions, as the most likely to bear fruit -- or prove fruitless -- in the shortest amount of time.

     Wesley Johnston

Background Details
I am attaching the two best maps that we have to help us.
1 - The top map is from my book on the 7th Armored Division in August 1944.
2 - The bottom map is Hubert Mazure's map from his book "L'Armée Patton dans l'Aube."

Top Map - Ruling Out 7th Armored Division
The top map shows the extreme north and south limits of the six-column front of 7th Armored Division. Combat Command "A" had three task forces, traveling on roughly parallel routes, and Combat Command "B" had three task forces traveling on roughly parallel routes. The reserve Combat Command "R" had two task forces, one of which followed CCA and one of which followed CCB. The lines on the map are the extreme left-most and right-most of the six task forces, thus showing the limits of the entire 7th Armored Division's route. More detail is known of the CCB route, which is why more towns are shown. As the map shows, the right-most column passed to the north of Donnemarie, moving through Maison-Rouge and Vulaines and then turning north to bypass Provins.

The CCR task force following CCB was Task Force Wemple, whose route is given in the 17th Tank Battalion After Action Report (Wemple commanded 17th Tank Bn): "Task Force A or Task Force Wemple left the assembly area in vicinity of Chapelle-Gauthier at 1835, 27 August, 1944 and proceeded along the route Fountainelles, Nangis, Moison-Rouge, Vulaines, Marolles, Maptery, going into an assembly position near St. Genest at 0100, 28 August, 1944. The town of Provins was by passed because of strong enemy forces there.Task Force A or Task Force Wemple left the assembly area in vicinity of Chapelle-Gauthier at 1835, 27 August, 1944 and proceeded along the route Fountainelles, Nangis, Moison-Rouge, Vulaines, Marolles, Maptery, going into an assembly position near St. Genest at 0100, 28 August, 1944. The town of Provins was by passed because of strong enemy forces there."

Thus the trailing unit passed north of Donnemarie late on 27 August 1944. The lead unit had passed earlier in the day, according to the 7th Armored Division After Action Report: "Whether or not there were major elements in this area was not positively known but the presene  of enemy tanks in some strength in the vicinity of PROVINS-DONNEMARIA  was established. The threat of German units known to be south of the Division sector, and the threat of attack by units escaping from PARIS, on the north, was a constant concern for the Division in its advance. By nightfall, CCA had advanced as far as JOUYE  while CCB had cleared the town of NANGIS. At this time the Division was alerted for change in direction to the northeast to begin about 1200 Hours 27 August after CCB had cleared the town of PROVINS, and advanced as far as VILLENEAUXE."

So the lead elements passed north of Donnemarie by Noon on 27 August, and the trailing combat elements had passed by to the north by Midnight of 27 August. There may have been some very rear echelon units that passed later, but they would most likely have followed the same route and passed well to the north of Donnemarie.

Bottom Map -- Possibility of 5th Infantry Division -- or a XX Corps non-divisional unit
The bottom map shows the 5th Infantry Division's 2nd Infantry Regiment moving south of the Seine, reaching Bray-sur-Seine on 26 August. I am concerned about the dates on this map. It is clear from the After Action Reports above that the arrow showing 7th Armored Division moving north of Provins on 26 August is not correct for the bulk of the combat force, which did not move there until 27 August. If the other dates are similarly off by one day, then things fit together, but if the 5th Inf Div dates shown on the map are taken as accurate for the bulk of the combat troops, then 5th Inf Div would have been in positions that 7th Armored Division had not yet reached, which was almost certainly not the case, since the armor was used mostly to spearhead and the infantry to deal with the strongholds that the armor bypassed. Especially unlikely (unless a recon unit) is the dashed arrow that shows some element of 2nd Inf Rgt moving to Provins on 26 August. If the map shows recon units for the dates, then the dates may be accurate, but the 7th Armored Division combat troops definitely did not reach the area indicated on 26 August, as their own records show.

I have been guessing that 5th Inf Div probably had moved to this point on routes south of the Seine that roughly paralleled the west-to-east movement of 7th Armored Division -- and that the 5th Inf Div was moving in a wide front, just as 7th Armored Division was, perhaps two regiments leading, each with multiple task forces, and the other regiment in reserve. And 2nd Inf would have been the regiment on the left. In the full version of the map, it shows the 5th Infantry Division (except for that one dashed line to Provins) staying south of the Seine until they reach Nogent-sur-Seine, at which point the turned north and reached Sézanne, which the reserve Task Force Wemple of 7th Armored Division's CCR had already reached on the morning of 28 August. While the 10th Inf Rgt of the 5th Inf Div did clear Montereau on 24 August (I found this in Blumenson's Breakout & Pursuit, p. 586), I think it is still likely that their advance east from Montereau was south of the Seine. After Melun was secured, the boundaries of the zones was changed very greatly, so that 7AD was pushed southward from the area where they had crossed the Seine at Tilly. In fact, some of their elements had to go all the way down to Fontainbleau to cross the Seine and then travel back north on the east side of the Seine to get in place for the attack to the east. Significant shifts in zone boundaries from 25-28 August are an important factor in trying to figure out who liberated Preuilly.

It is the 27 August shift from west-east to north-south movement, as well as the movement of 5th Inf Div elements through some of the same places as 7th Armored Division that leads me to believe that the initial zones were 7AD north of the Seine (which is where we know they were) and 5AD south (which is where at least the 2nd Inf Rgt was according to Hubert Mazure's map) and that the zones then were changed at noon on 27 August (as reported in the 7AD text above) to north-south boundary lines, as the movement of the forces headed north. The Army would never have had 5th Armored Division forces reaching Sézanne while 7th Armored troops were still there: the zones would have been changed to place the town in 5ID's zone. Otherwise there would be not only traffic congestion but the possibility of friendly fire. And there is no 7AD record of any such meeting with 5AD, which surely would have raised ire on both sides and been noted. So once again, I find the movement of 5th Inf Div troops to Sézanne on 25 August almost certainly wrong, unless these were recon elements.

If the 2nd Inf Rgt did move on eastward to Bray and Nogent before crossing, as the map shows, then they would not likely have been the liberators of Preuilly, since they would not have been north of the Seine until crossing at Nogent (which presumably came about the same time as the 7AD direction changed at 1200 on 27 Aug). So both the 5th Inf Div and 7th Armd Div forces had already moved either north or south-and-then-east of Preuilly by the morning of 27 Aug.

This is why I suspect that Preuilly was liberated by a rear echelon unit of 5th Inf Div or a XX Corps non-divisional rear element -- or else by a recon unit much earlier in the day. And this points out a big hole in my August 1944 book: While I have records of many of the elements of 7AD in the book, I do not have the records of 87th Cavalry Reconnaisance Squadron, nor does the Aug 44 Morning Report microfilm that I have include