Wegekarte (attack plot)

[Markus Witt]

Below is a description of an attack that I carried out were I obtained target data by plotting. This is a somewhat realistic method used by actual Uboats. This is a bit more immersive than using the rec manual (I never use it), the only downside is that it is time consuming and a bit labour intensive. I share it as it might be of interest to some and it contains a lesson to be learned.

I'm in Planquadrat AM13 on my way to my patrol area with engines slow ahead on course 240 when at 2111 my watch crew spots smoke on the horizon, bearing 329.
I can't see it myself and at 2113 I ask for a new bearing and this time it is 327. This already tells me that the target is travelling easterly and at 2115 I change course to 180 (pointing the boat ahead of the targets assumed general course) in order to get closer and get a visual myself. A few minutes later I see smoke and a little later chimney and masts. Now I know I'm dealing with a freighter and I can begin to plot the target to obtain it's course and speed.

The first step is to establish a rough target course. I do this by plotting the target position on the map and guess were it is going based on possible destinations and change in bearing. Change in bearing tells me it is heading east and by looking at the map (see 1st attachment) I guesstimate it might be going towards the North Channel with a heading of ESE.

At 2130 I take a bearing with (rough) range estimate and plot target position in the map based on my own position and (see 2nd attachment, red is own vessel course, green target course). The next 1.5 hours I match course and speed with the target while keeping a rough constant range and take a range (estimated) and bearing every 10 minutes to plot the target position in the map. Based on this I determine a speed of 8 knots and a course of 105. (Actually I had already estimated these values around 2200.)

The plan is now to manuevre ahead of the target into position for a night surface attack and arrive there a bit after midnight (when it is fully dark). At 2300 I speed up to half ahead to get into position while continuing to take bearings on the target. This is were I make a crucial mistake. Based on my observations it seems the target has sped up to about 9.5 knots and this confuses me. If you look at the attack plot you can see why. The thin black line represents the original estimated course line of the target and the green line the actual course line. This shows that I constantly underestimated the range to target.

As long as you match course and speed and keep a constant range then the actual range does not matter when determining target speed. (between the bearing lines of 2130 and 2300 the distance travelled on both courselines is the same). However when you start overtaking the actual range does matter. (between the bearing lines of 2320 and 0000 the distance travelled on the black courseline is greater than on the green courseline). This is the mistake I made and the lesson learned.

So at this point I am not sure anymore about target course and speed and I am a bit tired of the chase. At 0015 I decide it's time to attack and change course to 195 to set up a 0 degree gyro angle shot based on the original calculated target course and speed. During the approach I change my mind and start adjusting speed to keep a constant bearing to the target and set up a constant bearing shot as I am still not sure of target course and speed as the target is further away than expected. As the target gets closer I become convinced again that the target is still on a course of 105-110 and I go back to the zero gyro angle shot. By now the target is getting really close and I intent to go to dead slow ahead to allow the target to pass ahead of me and fire my torpedoes. Somehow I missclick with the mouse and continue at high speed without realising it.

I am now completely target fixated looking through the UZO and waiting for the target to pass the crosshair so I can fire my torpedoes. When the target passes the crosshair it completely fills up the UZO and I fire 2 torpedoes. As I "exit" the UZO I realise I am right on top of the target vessel and am still travelling at high speed. I give hard to starboard and go full astern to avoid a collision, but it is too late and I strike the freighter's stern. A few seconds later search lights from the (Icelandic) freighter light me up and they shout something at me in Icelandic which I can't understand, but that's probably for the best as it does not sound very friendly.

As we were so close to the target both torpedoes couldn't have missed but they did not detonate as they did not have enough time to arm before reaching the target. Probably lucky for me as I would have blown up as well being so close. Looking at the final plot, the position of the collision tells me the original calculated course and speed were correct and this should have been an easy kill.
Embarrassed, I speed away and continue to proceed towards my patrol area. In the meantime I contemplate how to explain to Dönitz why there is a dent in my bow and why I am missing 2 torpedoes. I hope he doesn't charge me for them.