How Submarines Shattered the Rules of War

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1:00Welcome in everyone. It is really great to have you with us today. Absolutely. Thrilled to be here. Whether you are prepping for a strategic meeting, maybe catching up on some military history, or you just want to understand the underlying mechanics of how the modern world was shaped, you are in the exact right place. That's right. Today, we're pulling from a really comprehensive Wikipedia article. It covers the history, the governing rules, and the major global instances of unrestricted submarine warfare. I have you topic, but a vital one. Very. And our mission for this deep dive is to understand how a single naval tactic did far more than just change the way ships engaged at sea. Yeah, it went way beyond that. Exactly. It literally rewrote global alliances, it factored international law, and it pulled entirely new super power nations into world wars. We are looking at a profound historical example of technology moving much, much faster than the law could keep up. That is the crucial lens to view this through.

2:00I mean, this isn't merely a chronicle of maritime history or, you know, ships sinking in the dark. It is a story about the fundamental tension between emerging disruptive technology and the outdated legacy rules of war. The old paradigm. Exactly. When a new weapon arrives that completely shatters that old paradigm, we usually see a period of intense diplomatic denial. And that is inevitably followed by catastrophic global consequences. Okay, let's unpack this by looking at the baseline. Before submarines completely altered the naval landscape, maritime warfare operated under a very specific set of customary laws. The old rules of the sea. Right. The 1899 Hague Convention formally codified a lot of these limitations, but the framework itself had actually existed for centuries. It was a system built around cruiser rules, or as they were often called in legal frameworks, prize rules. Right. The core concept was actually pretty straightforward, enemy warships, always fair game. But civilian and neutral merchant ships were protected by these incredibly strict protocols.

3:03Yeah, under those traditional customary laws, a warship commander couldn't simply just open fire on a merchant vessel. That was a huge violation. So what do they have to do? They were legally obligated to execute what are known as visit and search protocols. It is essentially a maritime traffic stop. Exactly like a traffic stop, but carrying massive legal weight, if a cruiser intercepted a civilian or a neutral ship, they could only interfere with its voyage if it was carrying contraband. And that required actually distinguishing between types of cargo. Right. You had absolute contraband like munitions, weapons, that sort of thing. Okay. And then conditional contraband like food or fuel. But even if they found something. Even if the boarding party found prohibited cargo from a publicly announced list, they still couldn't just sink the ship with the crew aboard. Why? Customary maritime law dictated that the attacking ship had to ensure the safe evacuation of the merchant crew before destroying the vessel. Which makes sense on paper, but reading through the sources, this entire legal framework relied on a very specific power dynamic.

4:07Totally. It was designed entirely for surface ships. Right. A large, heavily armed cruiser could effortlessly pull alongside a completely defenseless merchant ship, fire a warning shot across the bow, and basically dictate terms. The overwhelming asymmetry and firepower made that whole visit and search protocol possible. But the arrival of the submarine completely inverted that tactical dynamic. Completely inverted it. And the irony here is that early submarines were actually incredibly fragile machines. I think we often picture modern nuclear powered Leviathan's operating deep underwater for months. Oh yeah, not even close. Right. The early 20th century submarine was essentially a highly vulnerable torpedo boat that possessed a temporary ability to submerge. Their battery life was incredibly limited. Their underwater speed was painfully slow. And critically, their hulls were completely unarmored. So they were sitting ducks on the surface? Exactly. If an early submarine surface to conduct a visit and search protocol, a single well-placed shot from a deck gun.

5:09Even a small one. Even a small caliber weapon mounted on a merchant ship could easily pierce the pressure hull and send that submarine straight to the bottom. So how did those severe physical limitations force naval commanders to reconsider these polite rules of engagement? Well, it basically made the traditional rules a death sentence for the submarine crew. For a submarine, it's only true taxical advantage is stealth. Launching a torpedo well submerged without offering any prior warning was infinitely safer. But doing so meant completely discarding the cruiser rule. Right. Because a sudden submerged strike completely removes any opportunity for the target to be searched to surrender or for that civilian crew to safely evacuate. That tactical reality brings us directly to the Imperial German Navy at the outbreak of World War One. Yes, a very tense situation. They possess this new technology, but they face intense internal pressure. The German army is bogged down in this massive continental struggle

6:09and high level officials in the Navy are facing severe public and political criticism for just sitting there. For their relative inactivity, yeah. They desperately needed to demonstrate their strategic value. And that institutional desperation is the absolute perfect catalyst for radical military solutions. Which explains the entrance of two key figures, Admiral Terpitz and Admiral von Poel. Right. Boyed by a handful of early tactical successes, they approached the German high command with a pretty radical proposal. They advocated for giving you boats a totally free hand to attack shipping without restrictions. A massive escalation. And they boldly promised that this unrestricted tactic would create a shock effect so profound that it could force Britain into a conciliatory mood in as few as six weeks. Which was an astonishingly audacious claim, especially when you look at the numbers. Exactly, particularly when analyzing the actual naval order of battle at the time. Admiral Terpitz was aggressively pitching these submarines as

7:10miracle weapons to both the military leadership and the public impress interviews. But in reality. In reality, the Imperial German Navy had an extremely limited number of viewboats actually available for operational deployment. It was a massive strategic bluff. They were banking entirely on the psychological terror of the weapon. They theorized that the sheer unpredictability of ships being destroyed without any warning would paralyze maritime trade. Merchant captains would just refuse to sail out of pure fear. Right. And as for the diplomatic fallout with neutral countries, which is a huge risk, the German naval command calculated that neutral nations would ultimately accept the submarine campaign as a proportional and reasonable reprisal for the devastating naval blockade that the British had already imposed on Germany. This is a very calculated rationalization. And it worked internally. Convince by this logic, Chancellor Bethman Hallweg formally approved the strategy on February 1, 1915. And the execution of that 1915 campaign serves as a fascinating case study

8:12in how the fog of war intentionally blurs the lines of international law. Because the sources reveal that this initial campaign wasn't technically fully unrestricted, was it? Not on paper, no. The official diplomatic stance communicated to the world was that neutral shipping was not to be targeted. Officially, the crosshairs were only on allied vessels. Furthermore, a lot of the veteran German submarine commanders, these were career naval officers, deeply steeped in the maritime traditions of the cruiser rules. They voluntarily chose to continue operating under the old protocols. Really? Yeah, they took on those massive tactical risks surfacing their vulnerable boats just to give warnings and allow crews to evacuate. But the internal directives from the German Admiralty told a completely different story. Oh, absolutely. Secretly, the Admiralty was heavily encouraging its U-boat commanders to attack while submerged and to actively minimize their efforts at target identification. And the underlying logic there was brutal. They figured that the accidental sinking of neutral ships would serve as a highly effective psychological deterrent.

9:14Essentially frightening neutral fleets away from European waters entirely. It was a deeply cynical operational strategy, basically leveraging civilian collateral damage as a primary weapon of war. And while the campaign fundamentally failed to disrupt Britain's maritime logistics network to the degree Admiral Terpits had promised, the human cost was just severe. Devastee. That human cost reached a massive global flashpoint on May 7, 1915. A German U-boat, the U-20, deliberately fired a torpedo into the British Karnard luxury liner, the RMS, Lucettania. A horrific event. It sank in a matter of minutes, resulting in the deaths of nearly 1200 people, including over 100 American passengers. What's fascinating here is the sheer velocity of the geopolitical backlash. It was instant. The German high command fundamentally miscalculated how an emerging neutral superpower would react to the sudden violent deaths of its citizens on the open ocean. Right. The diplomatic outrage radiating from the United States

10:16was immediate and explosive. The pressure forced German Chancellor Bethman Hollig to directly intervene, actually going against the wishes of his own naval commanders. He had to do something to stop the bleeding, diplomatically speaking. Exactly. He secured a secret directive that explicitly prohibited U-boats from targeting passenger vessels. And then, following another severe diplomatic crisis, sparked by the sinking of the British liner Arabic in August 1915. Germany was forced to formally and publicly suspend the unrestricted submarine campaign entirely. Right. By 1916, the U-boat fleet was officially ordered to operate strictly under the traditional prize rules again. And a look at the operational data from the time shows that the vast majority of submarine attacks in 1916 were indeed conducted on the surface. So the diplomatic guardrails seem to have held? For a moment, yes. However, the sheer lethality and tactical advantage of this emerged to attack remain this overwhelming temptation. Especially as the war of attrition on the western front

11:16just continued to grind down the German state. Exactly. Here's where it gets really interesting. In early 1917, Admiral Henning von Holtzendorf, the chief of the Imperial Admiralty staff, presented a new memorandum to the German high command. And this was a game changer. He argued aggressively for the reinstatement of unrestricted submarine warfare, but on a dramatically larger scale than that 1915 campaign. He presented this as the singular definitive method to inflict tonnage starvation on the British Empire and force a surrender. We are looking at one of the most consequential, heavily calculated risks in the entire history of military strategy. No exaggeration. The German high command understood clearly that authorizing this campaign meant crossing a definitive red line. They knew with near absolute certainty that resuming unrestricted attacks would trigger a declaration of war from the United States. So knowing the massive industrial capacity of the US, how did the German Admiralty possibly justify taking that mathematical gamble? They relied on a very strict logistical timeline.

12:19Holtzendorf's memorandum argued that a massive unrestricted U-boat offensive would sink enough British shipping tonnage to force a complete collapse of the UK economy within five to six months. Very tight window. Very tight. They calculated that the United States military mobilization, training, and transatlantic deployment would simply be too slow. So it was a race. Exactly. The gamble was that Germany could strangle Britain and secure victory on the continent before American expeditionary forces could arrive in sufficient numbers to actually alter the balance of power. The decision was made. Germany unleashed the U-boats. And just as they predicted, it served as a massive trigger mechanism. It absolutely did. When combined with the public exposure of the Zimmerman Telegram where Germany actively proposed a military alliance with Mexico against the US, the resumption of unrestricted submarine warfare officially ended American neutrality. The United States entered World War I. I want you to consider the immense historical weight of this strategic gamble.

13:21A singular tactical decision regarding the deployment parameters of a specific maritime vessel made by naval planners in a war room. Effectively sealed the trajectory of the entire global conflict. Incredible. It pulled a rising industrial superpower right into the European theater and permanently altered the geopolitical landscape of the 20th century. And the bitter irony for the German Admiralty was that their timeline completely failed. Right. The U-bo campaign caused immense destruction. No doubt about it. But it did not break the British logistics network in time. And the American forces did arrive. They certainly did. So World War I eventually concludes leaving behind unprecedented devastation. And in the aftermath, the international community was deeply, deeply traumatized by the memory of the Lucitania and just the sheer ruthlessness of the U-boat campaigns. The psychological scar was massive. Right. There was a massive diplomatic push to ensure submarines could never again be used as weapons of commerce rating. And this led directly to the 1922 Washington Treaty

14:22on poison gas and submarines. And the objective of that treaty was crystal clear to impose such severe operational restrictions on submarines that they would be rendered strategically useless against merchant shipping. It was signed by major naval powers, including the United States, the United Kingdom, Japan, France, and Italy. But the fatal flaw of the Washington Treaty was a procedural one. Yes, it required unanimous ratification to enter into international law. And France, looking at its own maritime defense strategy, viewed the submarine as the ultimate asymmetric weapon. A poor man's navy. Exactly. A way to defend its coastlines against the much larger surface flutes of its rivals. So France refused to ratify the treaty, rendering the sweeping prohibitions entirely dead on arrival. The international community attempted to close the gap again later with the 1936 London Protocol on submarine warfare. Right, trying again. This agreement was much more specific. It mandated that submarines strictly adhere to the traditional prize rules.

15:22If a submarine intended to sink a merchant vessel, it was legally required to surface, conduct a visit and search, and critically place the civilian crew in a place of safety before destroying the ship. But the sources highlight just how quickly that legal framework began to crumble when confronted with the actual realities of naval technology. If we connect this to the bigger picture of international law, we see a persistent vulnerability and that is ambiguity. Ambiguity in the text. Right. Legal scholars frequently note that nations will intentionally engineer loopholes or tolerate vague language and treaties to protect their own future's strategic flexibility. Especially concerning dual use technology. Exactly. And that ambiguity became glaringly obvious when trying to define what actually constituted a merchant ship. Yes. Because remembering the devastating impact of the U-boats in WWI, Britain adopted a policy of heavily arming its civilian merchant vessels with defensive deck guns. Which creates an immediate paradox in the laws of war. Yeah.

16:23The line between a protected non-combatant and an active combatant completely blurs. Right. If a submarine commander surfaces to legally execute a visit and search protocol, and the supposedly protected merchant vessel, immediately opens fire with a naval gun. Which they did. The legal protections become a fatal liability for the submarine. The complexities compound even more when we look at that place of safety requirement. Let's just pause and consider the practical physical reality of that rule. It's almost absurd. A standard WWII era submarine barely had enough internal volume for its own crew. It's torpedoes and its provisions. Taking on dozens of captured civilian sailors from a sunken freighter was physically impossible. Because taking prisoners aboard was impossible, the legal alternative was to force the merchant crews into their own emergency lifeboats before sinking the ship. But think about what that means. We really must reflect on the grim reality of this legal fiction. Forcing a civilian crew into wooden robots in the middle of the North Atlantic in January,

17:23hundreds of miles with a nearest coastline. That is not providing a place of safety. No, it is a delayed death sentence disguised as legal compliance. The entire framework was an illusion. An illusion that shattered entirely with the outbreak of WWII. Prior to the conflict, an incredible 48 states had signed on to the prohibitions against unrestricted submarine warfare, including all the major global powers. Yet the very moment national survival was truly on the line, those treaty obligations were rapidly and systematically abandoned by every single belligerent nation. The source outlines four major historical campaigns of unrestricted submarine warfare. The first was the WWI campaign we just discussed. Right. The second was the Battle of the Atlantic, stretching from 1939 to 1945. Germany discarded the international rules immediately upon the outbreak of war, officially issuing war order number 154, which explicitly authorized unrestricted attacks. And the tactical evolution in the Atlantic was profound, with submarines operating in coordinated groups

18:24to hunt down maritime logistics networks. So wolf packs. Exactly. Then the third major campaign occurred in the Baltic Sea, primarily from 1942 onwards. This was waged between Nazi Germany and the Soviet Union on the eastern front, utilizing the exact same unrestricted doctrines. And the fourth campaign took place in the Pacific theater, waged primarily by the United States Navy against the Japanese Empire. Yes. And it is crucial to highlight the historical irony here. The United States, the nation that had entered World War I, largely out of moral and political outrage over unrestricted submarine warfare, abandoned the restrictions from the very first hours of the Pacific War. It was an immediate shift. Following the attack on Pearl Harbor, the order for unrestricted submarine warfare against Japan was issued without hesitation. Both the British Empire and the Atlantic and the Japanese Empire and the Pacific relied heavily on extended, incredibly fragile, maritime logistics networks to transport raw materials and sustain their war machines. Right. They were island nations, which made them uniquely vulnerable

19:26to the strategy of tonnage starvation. And the data reveals a truly staggering conclusion. Despite the historical focus on German U-boats and the battle of the Atlantic, the most devastatingly successful campaign of unrestricted submarine warfare in history was executed by the United States. The U.S. Pacific submarine fleet operated with just lethal efficiency, targeting vital shipments of oil, boxite, and raw materials before they could even reach Japanese factories and working in tandem with extensive naval minefields. American submarines methodically choked off the Japanese home islands. The numbers are wild. By the end of the war, they had reduced the Japanese merchant fleet to less than a quarter of its initial tonnage. It was a masterclass in asymmetric naval warfare, utilizing the exact doctrine the nation had once condemned as a violation of international law. So what does this all mean? When we trace the arc of this history, we see a naval tactic born out of sheer institutional desperation in WWE. Right.

20:26It was a technological leap that broke customer maritime law sparked enough outrage to pull the United States into a global conflict and survived decades of intense diplomatic efforts to ban it. It survived all of it. Yet, when the ultimate test of World War II arrived, unrestricted submarine warfare became the standard operating procedure for all major powers, ultimately being perfected by the very nation that first went to war to starve it. It is a sobering testament to the brutal pragmatism of total war. But this raises an important question for you to consider long after this deep dive ends. What's that? The cruiser rules we examined failed so spectacularly because they were written for an era of surface ships. They completely failed to account for the stealth capabilities of early submarines. The technology just outpaced the law. Exactly. So today, as modern militaries rapidly developed fully autonomous drones, AI-driven targeting systems and next-generation stealth weapons, we have to ask ourselves, are our current international laws of war about to become just as obsolete

21:28and just as heavily tested as the rules of the sea were in 1915? That is a fascinating, incredibly complex thought to leave off on. We want to thank you for joining us today, as we navigated this impactful history. It is deep dives like this that really remind us why analyzing the past is the most effective way to understand the architecture of our future. Thank you for listening, and we will catch you on the next deep dive. Finding great candidates to hire can be like, well, trying to find a needle in a haystack. Sure, you can post your job to some job board, but then all you can do is hope the right person comes along, which is why you should try Zip Recruiter for free. At ziprecruiter.com slash zip. Zip Recruiter doesn't depend on candidates finding you. It finds them for you. It's powerful technology identifies people with the right experience and actively invites them to apply to your job. You get qualified candidates fast, so while other companies might deliver a lot of, hey, Zip Recruiter, find you what you're looking for. The needle in the haystack. See why four out of five employers

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