U-boats
Submarines
German submarines were a threat to shipping on the North Sea during WW1. Many merchant ships were torpedoed or sunk by the Germans. Does that mean that submarines are a likely cause also to the loss of Mary? Intially I thought so, but that theory becomes less probable the more I learn.
The Swedish book "UNDERVATTENSBÅTSKRIGET - Med huvudsaklig hänsyn till krigsskådeplatsen i Nordsjön under världskriget 1914-1918" turned out to be gold mine of information regarding the submarine war. With details of the marine forces and their strategies it contains almost day to day records of the war. This book gave me perspective to Mary's voyage in relation to the calendar of the sea war. Below is information from this book and my conclusions regarding s/s Mary.
The title translates into "The submarine war - with focus on the war theatre in the North Sea during the World War 1914-1918". The book was written by Naval Captain Arthur Örnberg and issued in Stockholm 1920.
Three phases
The author divides the North Sea submarine war into three phases:
1. First phase 1 AUG 1914 - 18 FEB 1915
2. The restricted submarine war 18 FEB 1915 - 31 JAN 1917
3. The unrestricted submarine war 1 FEB1917 - End of war
Conclusion
Mary left Seaham Harbour on 16 FEB 1915, which was only two days before the beginning of "the restricted submarine war", but still within the "First phase". As this was in the transition period between the 1st and 2nd phases it can be of interest to find out how the sea war developed, day by day, when Mary began her last voyage,
First phase
1AUG 1914 - 18FEB 1915
In this period the German navy kept its surface ships in harbour while the British maintained a blockade against the German harbours. With surface ships in harbour, the Germans used approximately 23 submarines in the North Sea to harass the British navy - both at sea and in the British harbours. All in all, this was a trial period where both forces tested material, personell and tactics. The losses were limited on both sides.
Although a few British merchant ships were sunk, there was little threat to merchant ships from neutral states.
Conclusion
Assuming that Mary had made a number of voyages to England in this period, we can guess (speculate) that her crew had become somewhat "accustomed" to sharing the North Sea with naval forces at war. With Mary flying the neutral Swedish flag the crew probably regarded the risks as acceptable.
Transition into the restricted submarine war
04FEB -18FEB 1915
On 04FEB Germany issued "Declaration of Naval Blockade Against Shipping to Britain". Enemy merchant ships would be destroyed and also merchant ships of neutral states were under risk. This unrestricted submarine war should begin 18FEB,
On 11FEB the United States sent a protest to Germany claiming that US interests must be respected.
On 15FEB the Kaiser, after consideration of the US protest, issued an order that the unrestricted submarine war should be postponed until further and not commenced on 18FEB as previously declared. At the same time it was attempted to send wireless telegrams to all dispatched submarines that merchant ships under neutral flags must not be attacked. However, this order did not reach all the dispatched submarines. Submarines not yet dispatched were ordered to remain in their harbours.
On 18FEB the Germans decided to secure free passage of Swedish and Danish shipes in a channel between Lindesnes (southern tip of Norway) and Tyne.
On 20FEB the Germans launched the restricted submarine war. Ships under US or Italian flags were not to be intercepted in the war zone. From this day the focus of the German submarines was moved from the enemy's naval forces at sea to the enemy's commercial trade and communications over the North Sea.
Conclusion
Mary's departure from Seaham Harbour on 16FEB certainly took place during days of a developing drama affecting the safety on the North Sea. We do not know to what extent the crew of Mary was aware of these developments. Most probably they were aware of the declaration issued on 04FEB stating that an unrestricted submarine war against merchant traffic should begin 18FEB. Were they also aware of the start of this war being postponed? Only afterwards can we conclude that the Germans tried to exclude neutral states from the war actions beginning 18FEB.
Could this threat have forced them to make a hasty departure from Seaham Harbour? Was it more important to leave as soon as possible than to secure the seaworthiness of their ship and make all requied preparations for the voyage. We can only speculate.
As the contra order, issued on 15FEB, did not reach all submarines there were submarines out there acting as if attacks on neutral ships were permitted. However, these submarines also operated under the order that this unrestricted war should begin on 18FEB and, thus, they would probably not attack a Swedish ship before that date.
Restricted submarine war
18FEB 1915 - 31JAN 1917
Initially Germany did not achieve the intended impact on British shipping due to lack of sufficent number of submarines and the restrictions against attacks on neutral ships. On the 18th and 24th of April the German war kabinett repeated the orders not to attack ships from neutral nations.
During the following months the number of sunken merchant ships increased and also ships from neutral nations were attacked and sunk. The Germans explained this by claiming that the British disguised their ships by carrying false national flags. They gave example of 66 cases where Bristish merchant ships carried flags of neutral nations and in 16 of those it was Swedish flags.
In the beginning of 1916, the number of German submarines had increased to 65. After the battle of Jutland in May 1916 the activity of German submarines increased significantly and at the beginning of 1917 they constituted a real threat to the British domination over the North Sea and the ability of the British to maintain the blockade against the German "Hochseeflotte".
Conclusion
Mary may have seen the very first days of this period. However, for the major part of this period Mary was already at the bottom of the sea.