Tham khảo đoạn văn dưới đây và sau đó trả lời câu hỏi sau đó bằng ngôn ngữ tương tự như đoạn văn:

Đoạn: After the failure of the Revolutions of 1848, Adalbert was able to resume his plans for the establishment of a Prussian Navy.  He began with the construction of warships and naval education and training.  From the middle of the 1850s, one could find Prussian corvettes and frigates upon all the world’s seas.

Câu hỏi: When were the Revolutions?
1848