There is a long history of the connection between music and politics, particularly political expression in music. This expression can use anti-establishment or protest themes, including anti-war songs, although pro-establishment ideas are also used, for example in national anthems, patriotic songs, and political campaigns. Many of these types of songs could be described as topical songs. Unlike many other types of music, political music is not usually ambiguous, and is used to portray a specific political message. While the political message in political music is apparent, it is usually in the political context of the time it was made–which makes understanding the historical events and time that inspired the music essential to fully understanding the message in the music. Since political music is meant to be heard by the people, it is often meant to be popular.