Why did the retention of Gibraltar become significant in the years 1869/1875?

The retention of Gibraltar became significant in the years 1869/1875 primarily due to the opening of the Suez Canal. The Suez Canal, completed in 1869, dramatically altered global trade routes by providing a direct maritime passage between Europe and Asia, which significantly reduced travel time for ships. Gibraltar, positioned at the entrance of the Mediterranean Sea, became a crucial naval and military point for controlling access to the canal and protecting trade routes.

As trade through the Suez Canal increased, the strategic military importance of Gibraltar also escalated. It served as a coaling station and a refueling point for naval ships traveling to and from the Indian Ocean and beyond. This geographical advantage meant that whoever controlled Gibraltar had significant influence over maritime traffic heading to the canal, making its retention vital for any colonial or naval power at the time, particularly for the British Empire.

The other factors mentioned, such as the discovery of oil, increased military tensions in Europe, and the rise of colonial competition, may also have played roles in the broader geopolitical landscape, but they were not as directly influential to the strategic significance of Gibraltar specifically related to the Suez Canal opening as the latter was.