Three white soldiers is a three day trend reversal pattern. 
This  pattern happens after a downtrend. It consists of three large bullish candlesticks with each of them closing higher than the previous one. Each of these candlesticks should open within the body of the previous one. The upper wicks should be very small or non-existing 

Psychology of Three white soldierspattern is that  during downtrend one large bodied bullish candlestick on Day 1 indicates  that bulls managed to keep the price of the security at high which indicates strength. This is repeated on Day 2 and Day 3. As Open, High, Low and close of these bullish candlesticks are higher than the previous days candlesticks, it indicates the strength of bullish momentum and signals that prices are moving up. 

Three White Soldiers -1

 

Practice Three White Soldiers – Beginner

Practice Three White Soldiers – Intermediate

Practice Three White Soldiers – Advanced