One of the key political questions scholars have debated while studying Hincmars De Divortio Lotharii regis et Teutberga reginae is the extent to which Hincmar was simply advancing Charles the Balds cause in giving his advice on the case. Was Charles the Bald hoping to take over his nephews kingdom and was Hincmar helping him do that?
The evidence that Charles the Bald was hoping to take advantage of the situation is fairly strong: the Annales Bertiniani for 860 (written in Charles own kingdom) say that Lothar II made an alliance with Louis the German (his other uncle) fearing his uncle Charles. This is undated, but recorded by Prudentius after the meeting of the three kings at Koblenz in June, so probably subsequent to that, which means that Lothar had had a good chance to size up Charles intentions. Given that all Carolingian kings were serial grabbers of other rulers territories, Charles probably was hoping to get something out of Lothars problems. The question is whether Hincmar was helping him.
The argument made by those thinking the worst of Hincmar (that he was arguing dishonestly for political ends), is that he (and Charles the Bald) were forcing Lothar to remain married to a sterile woman (Theutberga), so he could not hope to have any heirs, leaving his kingdom free after his death. Several counter-arguments have been made. There was no suggestion in 860, when Hincmar wrote De Divortio, that Theutberga was sterile; indeed, one of the many charges against in her in 860 was that shed had an abortion. The allegations by Lothars supporters that she was sterile were only made after 860. Secondly, Hincmar didnt argue that Lothar had to remain married to Theutberga in De Divortio, but that her case had to be tried again.
Also, (though this hasnt been pointed out before, as far as I know), why should Charles the Bald have presumed he would outlive Lothar, who was about 12 years his junior? It is only because Lothar II died young (aged around 34) that Charles and even Louis the German outlived him. If Lothar had lived to be 60 (as was perfectly possible, given that his father, grandfather and great-grandfather all did so), he could have been challenging Charles the Fats right to be emperor of all Francia in the 880s after the death of Charles the Bald, Louis the German and several of their descendents.
Does this put Hincmar (if not Charles the Bald) in the clear? Not necessarily, I now think. There are two interesting facts when you start looking carefully at the chronology of the case: in 860 both Theutberga and Hubert (her brother) fled to Charles the Balds kingdom. Hubert was there by the time Hincmar was writing the first part of De Divortio in the summer of 860, while Theutberga probably came shortly after he wrote that. Their presence in West Francia is significant because of what Hincmar argued about the procedure of the case. As I discussed in a previous post, he thought that the judgements made against Theutberga at the two synods of Aachen were not valid. He also accepted the validity of the ordeal procedure that had taken place in 858 (by which Theutberga has been cleared). However, Hincmar did not say that therefore the matter could not be opened again. Instead he argued for both a secular placitum to hear the case and a general synod to discuss wider issues.
If Hincmar had simply wanted to ensure that Lothar remained married to Theutberga he could have argued that the ordeal judgement of 858 was final. By arguing that another judgement could be made (and that if Theutberga had committed incest before her marriage, her marriage was not valid), he left at least the possibility of Lothar being able to remarry.
But the catch was that meant holding the secular placitum first, and Hincmar repeats several times that a valid judgement cant be made in absentia. He specifically says that the secular placitum needs to examine Hubert, as one of those accused of the crime. The principle of no judgement in absentia meant that the case would be in practice be suspended unless Hubert and Theutberga were in Lotharingia. Unlike synods, where judgements could be made by bishops from different realms, secular law courts operated only within a particular kingdom. And if Theutberga avoided the trial by escaping to another kingdom (an obvious strategy), as long as the case was suspended as result, Lothar was in limbo. He couldnt remarry before having a judgement on Theutberga, and he obviously couldnt meanwhile have any legitimate children with her.
There were agreements between the kingdoms for extraditing fugitives and Hincmar urges in De Divortio that Charles the Bald should stand by them. But in practice, such an extradition could be blocked for years without any serious difficulty. This was demonstrated by the case of Ingiltrude, which had just been raised at the meeting at Koblenz in June 860. Ingiltrude ran away from her Italian husband Count Boso with her lover, and managed to avoid returning to judgement or penance for at least 15 years, by taking refuge in other kingdoms (she was already up to 4 years in 860).
Whatever Hincmar might say about extradition, if his views were adopted, once Theutberga was in Charles the Balds kingdom, Charles held all the cards. If Charles sent back Hubert and Theutberga to Lothar, Lothar could then get his divorce via a rigged secular judgement. If he didnt, Lothar was definitely left heirless and unable to marry Waldrada. If Lothar wanted a legitimate marriage, he had to deal with Charles and provide some kind of incentive for handing over the fugitives. (A share in Provence would have been the obvious offer, since every Carolingian king was looking hopefully at the prospect of the young and sickly Charles of Provence dying soon).
As it turned out, Lothar didnt deal with Charles. Instead he and his bishops argued that the decisions at the synods of Aachen had been legitimate, and there was no need for a further trial. However, this got him entangled with the Pope, and he never managed to get the case sorted out.
Did Hincmar plan all this for Charles the Bald? Theres no proof of it: Hincmar could always come up with canonical reasons to support his suggestions, and we dont know the details of when and why Theutberga fled. The most we can say is that Hincmars suggestions in De Divortio, if adopted, would have respected divine law and benefited Charles, and that Hincmar would not have been displeased at the combination.