Until the 1870s British officials in China often acted without the Foreign Office's official consent because they could only communicate with London via mail. In the 1870s telegraph lines connected China to Europe. The Chinese government initially opposed foreign telegraph lines arguing that they undermined Chinese authority. British diplomats in China were also wary of the telegraph because it allowed the Foreign Office to intervene more quickly. From the 1880s the telegraph was increasingly used as an instrument of imperialism in China. The Boxer Rebellion in 1900 showed how important the telegraph had become as means of communication.