Complex sentence: The Mid-Canada Line, also known as the McGill Fence, was a line of radar stations across the "middle" of Canada intended to provide early warning of a Soviet bomber attack on North America, supplanting the less advanced Pinetree Line which was located further south.
Split into simpler sentences: The Mid-Canada Line, also known as the McGill Fence, was a line of radar stations across the "middle" of Canada intended to provide early warning of a Soviet bomber attack on North America. It was intended to supplanting the less advanced Pinetree Line which was located further south.