My impression is that Islamic history is on-topic and I've not seen an alternative stance on this. There's even a history tag (with 240 questions currently).
Moreover, my experience suggests questions about Islamic history are reasonably well-received here. Being historical, such questions tend to avoid the pitfalls when asking more personal question.
A similar meta question is Islamic history, on topic? The top answer writes:
I don't see why Islamic history should be off-topic, unless it is about sectarianism, which is off-topic.
As far as "history that involves Muslims" goes, I would have to give that a big X. This is a site about Islam, not Muslims. So, questions of any kind about Muslims are off-topic. -- Dynamic
As far as I know, this still applies.
So the main catch is distinguishing Islamic history (on-topic) from history which happens to involve Islam (off-topic) and history which involves Muslims (off-topic). I don't believe the community has clearly identified a boundary here; it's probably not worthwhile at this point, since we're not being inundated with borderline questions.
Cultural effects on Islam. As long as it's primarily about Islam, it should be okay. We need to understand culture to understand the Qur'an, ahadith, and the sunnah.
Effects of a certain victory or defeat on Islam. Sounds on-topic; it's about Islam. There's even some tags: battle-of-karbala, battle-of-jamal.