Good questions! This is an area of hot debate right now, in large part due to some work being done right now in Uppsala and Stockholm on a particular grave from the Viking-Age trading town of Birka. I'd like to discuss this a bit and get into the meat of your questions, but for readers who want the quick and dirty, I'd recommend a twitter summary of "A female warrior confirmed by genomics", some objections blogged by Judith Jesch, and the researchers' response in the form of supporting information. Or you can keep reading below!

The grave in question is known as Bj 581. It was excavated back in 1878 by Hjalmar Stolpe, who is considered something of a father for Swedish archaeology. In the burial labeled Bj 581, Stolpe dug up bones and a bunch of artifacts which we would associate with warriors. The Swedish Historical Museum has helpfully posted all these things online.

A group of researchers, reassessing the Birka burials—there's over 3000, with about 1100 excavated—recently discovered that the bones of Bj 581 were female bones. They announced their discovery in a brief note in a scholarly journal, which quickly hit the popular press, including the Guardian. But other researchers had a lot of questions. The initial reaction was excited but mixed, as captured by this excellent twitter discussion (full of photos!) by Caitlin Green.

The biggest objections, posed by the eminent scholar Judith Jesch in an incisive blog post, were: (1) Stolpe's methods included dynamiting graves apart for rapid excavation, and at some point in the last 140 years, many of the bones and artifacts that he did manage to save got mixed up in the museum collections—Are these even the right bones? (2) It's a well-known axiom of archaeology that the dead don't bury themselves—Does putting weapon's in a female grave turn a woman into a warrior? And (3) Has this information—originally published in a note with the provocative title "A female viking warrior confirmed by genetics"—been properly presented?

The last question is still in process, and I won't pass judgment here, but as an academic, I'm happy to see some of the scholarly objections have recently been redressed with the informal release of supporting information. (I believe this was presented by Charlotte Hedenstierna-Jonson at a recent lecture at the University College of Dublin, but I'm not sure.) The researchers make the point that very few of the skeletons excavated by Stolpe had intact vertebrae. He drew intact vertebrae for Bj 581, intact vertebrae were included in the bones that are currently attributed to Bj 581, and at some early point in their curation (late 1800s?), someone inked "Bj 581" onto a number of the bones. It's still possible, of course, that somebody looked at Stolpe's drawings, found the closest bone box with a respectable number of vertebrae, and then relabeled them as Bj 581. But it seems more likely to me that these are the right bones. Although I can't pass judgement on the researchers' methods of analysis (which fall far beyond my expertise), I'm fairly satisfied that they've properly identified the bones that belonged to Bj 581 and that these are in fact the bones of a female.

The authors of the supplementary information also point to two other burials—both in Norway—where a woman appears to have been buried with warrior weapons. So this is a rare but not an isolated example of female bones buried with weapons. But how do we interpret these mixtures of female bones and typically male grave goods?

It's possible, of course, that these warrior grave goods belonged to these females in life and even that they used them as warriors. It's not necessarily likely, but women have recently graduated from the US Marine Infantry Officer Course and the US Army Ranger School. I think these modern women-warriors are more than adequate proof that females could similarly have excelled among the warriors of the Viking Age.

Note that I'm doing my best here (and not entirely succeeding) to distinguish between female, which refers to biological sex as we interpret it today, and woman, which is a term more closely related to identity and cultural performance. If these females were warriors, then they may have been thought of as if they were men in real and meaningful ways by their contemporaries. In this case, the females would likely have been completely integrated. There's absolutely no reason to assume that women were segregated into separate female fighting forces. We only have three of these burials, and at least in the case of Bj 581, the female with warrior goods was buried in a common cemetery right below the fort together with male warriors (as well as women and children). Bj 581 may have been an exceptional female, but if so, s/he wasn't seen as an outsider.

So finally, the big question: Is this actually evidence enough to support the image of female warlords seen in Vikings and in other places across the internet. Here's where I become a bit more cautious, and I hope the Swedish researchers take some time responding to Jesch's comments as they prepare a full publication of their findings on Bj 581. But in general, I'd say it's very possible, but not likely in large numbers, and even the female burials with weapons need not be considered as "typical" women-warriors. As you succinctly put it: "A female skeleton buried in a grave alongside weapons does not necessarily mean she was a warrior, let alone a warlord." Perhaps they were just regular women, buried with a husband's weapons. Or perhaps they were the last surviving members of a family and so were buried with all their warrior accoutrements that had belonged to their extinguished line. We simply don't know, and it would actually require a large comparative analysis of burial practices to come to these kinds of conclusions, rather than a narrow focus on a few exceptional graves.

Moreover, many of the social pressures that make some women want to join the military today need not have applied during the Viking Age. Women held a privileged role in Scandinavia, wearing fancy dress and flashy accessories while their men wore more subdued clothes with few ornaments. Women kept the keys to the larder, managing farms and consumables in a society for which agriculture—not pillaging—was always the cornerstone for survival. And in the much later sagas as well as in contemporary picture stones, it seems often to have been the women who compelled men to fight and brokered peace. Viking-Age women could certainly be strong and powerful, but they didn't need to play with shields and spears to prove it.