There’s a profound lack of clarity when it comes to Germany’s
knowledge of the past, including his own. That said, let’s go over a brief
run-down of what we know that he knows.

Knowledge of his
Past/ Ancestors + Fabrications:

Prussia is the one that tells Germany all about his past.
What makes lots of people, including me, believe that Prussia is hiding Germany’s
unconfirmed past as Holy Rome is that the stories he tells Germany are
inaccurate. He’s an unreliable story-teller. 

In this case, the stories have to do with Prussia’s own past, as he lies about how “cool” or “rugged” he used to be. Germany’s understanding of what Prussia used to be is very different from reality.

Regardless, Japan is the one who gives us the best insight on this, as
he’s able to pick up on the fact that Germany believes everything that he’s
told about the past.

On the other hand, what’s strange is in another strip where
Prussia begins telling Germany about his past, Germany is completely
uninterested. He’s more focused on chores than he is on his own genealogy.

There is no explicit discussion of Germany’s relation to
Germania either. It mostly focuses on his older brothers – the German states.

However, despite the inconsistencies in Germania’s relation
to Germany, recent strips claim that Germany is his son. Again, what I find
strange is that Germany doesn’t inquire about his past far enough to at least
know about Germania.

He knows about Rome and even encounters the latter when he
visits down from Heaven and yet there’s no interaction/ discussion of Germania.

I’m of the mindset that Hima’s left things unclear and
undetailed on purpose. That way, he has more leeway to work with if he wants to
confirm in later chapters that Germany is, in fact, Holy Rome. Please remember
that this is all theory, none of this is confirmed.

Research: 

Despite all this, Germany has been shown on several
occasions to possess knowledge about the past, full of holes and vague as it
may be when we do see this depicted.

He does a lot of research for someone that seems to be
uninterested in his past.

Ex: He has a deep interest in Roman culture and history.

Ex: He’s conducted research in fixing historical records of Ancient Rome to make the narratives more accurate.

Ex: He once referenced the Dancing Conference, which occurred
right after the Napoleonic Wars. The point to emphasize here is that Holy Rome
was dissolved because of Napoleon.

If he has knowledge
about this figure, it inevitably means that he’s aware of the Holy Roman
Empire (duh). Likewise, historically, he would have to given what the Third Reich was
predicated on reviving…

Lastly, what’s interesting is that despite his knowledge of
Roman History, Germany doesn’t know much about Italy’s past.

Ex: He does his initial research in finding out that Italy
is a descendant of Rome.

However, in modern strips, he’s surprised to find out that
Chibitalia was able to ward off the Ottoman Empire on his own. He’s so used to
seeing Italy as a ‘hetare’ that he can’t imagine him in any other way.

Has Germany Recovered Memories of His Past?

There are two theories that I have in making the assumption
that a) Germany is an amnesiac Holy Rome, and b) he’s gaining his memories.

One position I take is that Germany has already recovered
his memories of Holy Rome but refuses to acknowledge the past and doesn’t tell
anyone about this. This would explain his lack of interest when Prussia brings
up their past. He already knows but doesn’t want to confront it.

This is well substantiated given that Germany has a strong
belief in data, and doesn’t believe in the supernatural. Even though Holy Rome
didn’t die right after dissolution, the fact that he didn’t is unexplainable.

Germany is of a scientific mindset and would therefore
probably ride it off. It’s not something he would accept. The surprise at
Chibitalia’s strength in earlier panels is simply because Holy Rome never got
to see Italy be that strong.

The other position I take is that Germany is just beginning
to recover his memories of Holy Rome, having previously repressed them from
before to guard against being re-traumatized.

Ex: In Buon San Valentino, Germany’s stress causes him to
blackout. During this panic episode, fuzzy images of Chibitalia appear, almost
as if they were semi-inaccessible memories.

Ex: Germany is once depicted to be holding Chibitalia.
Take note of the question mark and the phrase “it’s me”. 

To me, this seems like
Chibitalia is an unconscious aspect of Germany’s mind trying to pierce his conscious memory.

Ex: There’s also the strange occurrence where a child that
looks exactly like Holy Rome/ Germany is pressing to be ‘acknowledged.’ From a
psychological lens, this would be interpreted as repressed memories of Germany’s
childhood trying to reach his conscious mind.

Ex: Germany’s love for Italian culture and life can be seen
as him unconsciously remembering how much Holy Rome wanted to have Chibitalia
be part of his house.

However you want to see it, you have to admit that the
amount of questions left unanswered with regards to Germany’s past is done for
a reason. We just don’t know why exactly that is just yet.