Borderlines explores the global map, one line at a time.

Here’s a bit of insight into the mind of a budding map-head. While my grade-school geography teacher attempted to stuff our heads with tables on the average rainfall in the Amazon and graphs on the relevance of the Donbas [1] for the Soviet economy, I kept staring at the page showing East Asia, wondering: Does Russia share a border with North Korea, or does China touch the sea?

The map stubbornly refused to yield enough detail for an answer. The line that defined China’s borders with North Korea and Russia was inked too thickly to determine whether there was a Chinese-Russian-North Korean tripoint on land (but very close to shore), or a Chinese (but very narrow) beachfront on the Sea of Japan [2]. Both options seemed bizarre, yet either would have obvious geopolitical implications: in the former case, Russia would have unimpeded traffic with North Korea; in the latter, China would have direct access to a strategic body of water.

Did the mapmakers deliberately gloss over the issue, not wanting to be bothered with such trivia [3]? It’s more likely that they too didn’t quite know where to draw the line: the last border disputes in the area, a region with some of the world’s tightest, most heavily policed borders, were settled less than a decade ago. Even then, the border is too intricate to display adequately on a small-scale map [4]; you can see it with a zoomable online map, but you have to get in pretty close to see what the dickens is going on. And even if the ultimate question finally gets answered, the bizarre shape of the border throws up a new one: How did this happen?

But to answer that first, nagging high-school question: Yes, Russia does border North Korea [5]. Not by much, and though the border is terrestrial rather than maritime, it’s not strictly speaking a land border, either. The border between Russia and North Korea runs down the middle of the Tumen River’s last 10 miles, as it meanders toward the sea.

Joe Burgess/The New York Times

Yet even a border this short, and between two non-warring neighbors, was until fairly recently subject to dispute. Treaties signed in 1985 and 1990 resolved the territorial issues. In the hope of placating the wily regime in Pyongyang, Moscow acceded to most of its demands: the handful of river islands in the Tumen’s final stretch were placed under North Korean control.

The tripoint with China, 10 miles north from the mouth of the river, was fixed to the satisfaction of all three parties only in June 2003, when North Korea, Russia and China signed a protocol to that effect in Beijing. North of this point, a curious Chinese salient, sometimes no more than a few hundred feet across, occupies the east bank of the Tumen, following its curves for maybe another 10 miles until it fans out into a broader swathe of Chinese territory. It’s almost as if that salient is China’s attempt to rip through the Russian Bubble Wrap that keeps it landlocked.

Farther up the Tumen, the border between China and North Korea is not without its problems [6], but its essence is a beautifully simple symmetry. The Sino-Korean border runs through the summit of Paektu-san, a mountain sacred to both Koreans and Manchu [7], and follows the course of two streams that spring from it: the Tumen and the Yalu, which heads west toward the Yellow Sea.

The real question, then, is how Russia managed to block China from getting valuable access to the Sea of Japan? The answer dates from a time when the geopolitical roles of China and Russia were reversed: in the 18th and 19th centuries, Russia was booming and confident, China weak and insecure. Russian settlers took possession of the fringes of the Chinese world, de facto annexations that were ratified by a series of “unequal treaties” [8], the Treaty of Aigun of 1858 and the Russo-Chinese Convention of Peking of 1860, which established the easternmost part of the present-day border between China and Russia [9]. This allowed Russia to develop Vladivostok, founded in 1859 not far from the present tripoint, as a naval hub for the Pacific.

But Vladivostok is not a year-round, warm-water port. So the Russians strong-armed the Chinese into leasing them Port Arthur (known today at Lushunkou), on the Liaodong Peninsula, which juts into the Yellow Sea west of the Korean Peninsula. Japan saw Russia’s expansion as a threat to its own imperial ambitions; it attacked and defeated the czar’s eastern army and navy in the short, sharp, shocking Russo-Japanese War, which announced Imperial Japan’s arrival on the stage of world powers.

For the first time in modern history, an Asian power had defeated a European one. Japan took over Russia’s lease of Port Arthur, annexed the southern half of Sakhalin Island and virtually annexed Korea (which it would do outright in 1910). Russian influence over Inner Manchuria ceded to Japanese influence. In 1932, the Japanese installed Pu Yi, the dethroned emperor of China, as ruler of the puppet state of Manchukuo [10], which they eventually would use as a springboard for invasions of the Soviet Union and China.

From 1932 to 1939, Japan used border disputes between Manchukuo and the Soviet Union (and Mongolia, in the Soviet orbit) to pick fights. Despite hundreds of incidents, the tensions never flared into all-out conflict, but the undeclared war did prove costly in lives. One of the worst incidents, in the summer of 1938, was the Battle of Lake Khasan, a small body of water near the tripoint.

The battle, which came almost seven years before Moscow formally declared war on Tokyo, was the result of a spectacular Soviet defection. A month earlier, Genrikh Lyushkov had crossed the border into Manchukuo, thus becoming the highest-ranking Soviet defector to date: not only was he the chief of the N.K.V.D. [11] in the Far East, but he also was a member of the Communist Party’s Central Committee. He had just been recalled to Moscow, and feared the fate he had bestowed on so many others, namely a show trial and then the firing squad.

To ingratiate himself with his would-be hosts, Lyushkov brought along detailed information on Soviet military strength in the Far East. Panicked by the beans Lyushkov had been spilling, the Soviets spruced up their border defenses. A few pillboxes west of Lake Khasan strayed into territory disputed by Manchukuo (based on its interpretation of the 1860 Convention of Peking). On July 29, 1938, Japanese and Manchukuo forces engaged the Soviets, advancing four miles into Soviet territory, but kicked out by Aug. 2 by a forceful Soviet pushback [12]. The battle had cost hundreds of lives on either side. In 1945, The Soviets would turn the tables on the Japanese and invade Manchukuo — this time with a lot more success.

Related More From Borderlines Read previous contributions to this series.

In the following years the Soviets made sure that Manchuria became an asset for the Chinese Communists in their struggle for power. But once Mao had succeeded in turning China red and after the Soviets left Manchuria in his care, the cross-border relations between the supposedly friendly Chinese and Soviet Communist regimes reverted to the tension that was built into the “unequal treaties” by their predecessor states. In mid-1969, both countries fought a brief border war over Zhenbao Island [13], along the Ussuri River halfway between Vladivostok and Khabarovsk, killing dozens of conscripts on either side.

Ironically, China and the Soviet Union didn’t resolve their border issues [14] until 1991, months before the Soviet Union itself would collapse. The final border runs along a series of rivers, though the last few hundred miles before it reaches the Tumen River it follows a zigzag pattern across land.

A newly independent Russia ratified the agreement in 1992. One important motif: Possession of the riverine islands would be determined by the thalweg principle, which places the border in rivers along the deepest, most navigable channel. This eventually meant the transfer of about 700 river islands on the Chinese side of the thalweg, which until then almost all had been under Soviet control — among them Zhenbao Island. Small border changes near the border tripoint disenclaved a small patch of Chinese territory lost on the bank of the Tumen. Also, Chinese boats would now be allowed to sail down the river to the Sea of Japan [15].

The capstone of the entire agreement was the precise location of the Sino-Russian border on the Tumen’s left bank. The 1860 Convention of Peking set it 15 miles north of the river’s mouth. It was later moved to 9 miles north of the estuary, in 1964 back again to 11 miles above the Tumen’s terminus. Confirmation of the Sino-Russian border finally allowed the demarcation of the tripoint with North Korea in 1998.

Careful not to step on too many Russian toes, the finalized border near the tripoint left the war cemetery for the Soviet dead of the Battle of Lake Khasan on the Russian side of the new border. Maybe someday the local authorities will have the opportunity to bury the body of what must be the last casualty of that battle, if they ever find it: Genrikh Lyushkov, who disappeared during the last days of World War II.

Frank Jacobs is a London-based author and blogger. He writes about cartography, but only the interesting bits.

[1] Short for Donetsk Basin, a mining area in eastern Ukraine. Soviet terminology had a penchant for portmanteaus (vide sovkhoz, Comintern, Gulag).

[2] The Japanese prefer this name, which is also widely accepted internationally, while Koreans call it the East Sea. For a similar controversy, see the Persian Gulf, often referred to as the Arabian Gulf by the Arab countries on its southern shore. This annoys the heck out of Iran.

[3] Almost literally, as trivia is named after the news and gossip exchanged at a trivium, a three-way crossroads.

[4] Counterintuitive terminology alert: a small-scale map shows a larger area, in lesser detail (e.g. 1:25,000,000), while a large-scale map shows a smaller area, in greater detail (e.g. 1:25,000).

[5] This brings the total of countries sharing a terrestrial border with Russia to 14 (the others being Norway, Finland, Estonia, Latvia, Lithuania, Poland, Belarus, Ukraine, Georgia, Azerbaijan, Kazakhstan, China and Mongolia). Only one other country borders as many other countries: China (Mongolia, Russia, North Korea, Vietnam, Laos, Burma/Myanmar, India, Bhutan, Nepal, Pakistan, Afghanistan, Tajikistan, Kyrgyzstan and Kazakhstan). If Russia hadn’t prevented China from gaining access to the Sea of Japan, it would have bordered only 13 countries and lost out to China, which would still have bordered 14.

[6] Minor border disputes, still outstanding, resulted in skirmishes between both countries’ armies in 1968 and 1969, although it must be said that the tension caused by the Cultural Revolution probably added fuel to the fire.

[7] Paektu-san (Korean) and Changbai Shan (Chinese) both mean something like “White-headed Mountain.” The 9,000-foot-high volcano is entwined with Korea’s founding myth. The god Hwanung descended from heaven onto the mountain, transformed the bear Ungnyeo into a woman and gave her a son, Tangun. In 2333 B.C., he founded Gojoseon, the first Korean kingdom. North Korean mythology plays into the magic mountain’s attraction by claiming that Kim Jong-il, the recently deceased Dear Leader, was born there. Most likely, he was born in exile, near Khabarovsk in Russia’s Far East.

[8] The accepted term for a whole shopping list of restrictive and adverse treaties imposed on China (but also Japan and Korea) from the 1840s to the early 20th century.

[9] Establishing what is now known as Russia’s Far East but is still referred to by some in China as Outer Manchuria. Basically, the Russian territory south of the Stanovoy Mountains, a 500-mile-long range that forms the watershed between the Arctic and Pacific Oceans and that until 1858 constituted the border between Russia and China.

[10] “Land of the Manchu.” Compare with the Mandarin for China: Zhongguo (“Land in the Middle”). Pu Yi’s Qing dynasty, which lasted from 1644 to 1912 and was the last imperial house to rule over China before it became a republic, was originally from Manchuria. Because of the Imperial Japanese use of the geonym, preferential description for Manchuria these days is simply “the Northeast” (Dongbei) or “the three Northeastern provinces” (i.e. Heilongjiang, Jilin and Liaoning).

[11] A secret police organization, predecessor of the KGB.

[12] Some reckon that that makes this the first battle in the Second World War lost by an Axis power.

[13] Damanskiy Island, in the Ussuri River.

[14] Chinese claims, based on the modern borders, pertained to 13,500 square miles of territory, mainly on the western stretch of the Sino-Soviet border (west of Mongolia).

[15] If only it weren’t too shallow for most ships.