Complex sentence: Since 1877 the Radical Party was active as a loose parliamentary group, emerged from The Extreme, which was later organised as a full-fledged party in 1904 under the leadership of Ettore Sacchi.
Split into simpler sentences: Since 1877 the Radical Party was active as a loose parliamentary group, emerged from The Extreme. The group was later organised as a full-fledged party in 1904 under the leadership of Ettore Sacchi.