Well, one issue at a time:
The last sentence of the 1st paragraph truncates the narrative by jumps from one subject (internal policy) to another (foreign policy), before falling from the sky after decades to following paragraph without even suggest the reason of 1920s military revolts (not to mention that even remotely touches the civilian ones).
To remedy the last flaw of this paragraph, and with citations (easy to check) in English (other section's defect: too many sources in Portuguese, one of them is not even specific to Brazilian history) and
before to deal with the 2nd paragraph [ one issue at a time ) ], I suggest to let the 1st paragraph fine and end the discussion about this paragraph, 
I propose that the mention concerning to changes of Brazil's boundaries  in the early 20th century (even because, the border issue of Acre, in addition to not being the only one of that era, contained in itself a military phase, among others, having not been characterized or reduced to a mere purchase...), be placed at the beginning of the 3rd paragraph in the foreign affairs: 
 "In foreign policy, the success in resolving border disputes with neighboring countries in the early years of the republican period,* was followed by a failed attempt to exert a prominent role in the League of Nations,* after its involvement in World War I.***" ; 
more or less eg as I had proposed, both with a neutral point of view and specific easily checking citations in english...

So, if you agree to it in relation to the 1st paragraph, I will talk about my suggestions of changes regarding the 2nd and 3rd paragraphs and (again) why of it...