On the morning of December 6, 1917, the French cargo ship SS Mont-Blanc collided with the Norwegian vessel SS Imo in the Halifax harbour causing a massive explosion, a tidal wave, and fires. Some 1800 people died and thousands more were injured. Destruction was widespread and unprecedented which caused tremendous local, national, and international outpouring of aid and support, as first responders acted swiftly. To this day, Nova Scotia continues to donate a Christmas tree to the city of Boston as a thank you for helping during the Halifax explosion. This explosion was the largest man-made explosion to occur before the dropping of atomic bombs during the Second World War.