Trendline broken to the downside. Bears may begin entering the market first in single file, then in larger numbers. As they enter, some bulls will start to watch instead of participate. When the bears become the dominant participant is when the correction will be in full force. Bulls (in this hypothetical situation) will not let them have it for very long. Mostly the bears are only allowed to nibble after impulse #3 before bulls decide they are ready to push the market higher again.