Why was Luodian important in the Battle of Shanghai?

Question

In the middle of the 3-month long Battle of Shanghai, the small town of Luodian on the outskirts of Shanghai saw some of the heaviest fighting. After Japanese troops made successful amphibious landings along the northern coast, many Chinese troops fell back to Luodian, and over a 10-day period the town was heavily contested and changed hands multiple times.

It's clear from many facts that this town was strategically important, but it's not clear why this is so. Consider this map (actually I couldn't find a good map, so Google Maps would do fine too):

• Wikipedia, and other sites, claim that Luodian was a strategically important transportation centre. Wikipedia specifically says that it connects "Baoshan, downtown Shanghai, Jiading, Songjiang and several other towns with highways". I can't find a contemporary map showing highways, but from the map the only connection would be between Jiading and Baoshan. Songjiang is not even on the map; it's too far to the south. Which important towns does Luodian connect?
• Shanghai lies on a peninsula at risk of being cut off, so the fighting at this stage was focused on cutting off transportation routes into Shanghai from the mainland. By far the most important links would be the two railways leading out of Shanghai, with the northern branch connecting to Suzhou and Nanjing beyond. Jiading is also somewhat important; there's a road going northwest from here parallel to the railway, meeting it eventually at Wuxi. Another important location would be Dachang, which is very close to this railway and was the communications hub for the Chinese forces. It's clear why Dachang would be important, which it was; it was the next site of heavy fighting after Luodian, and its loss forced the Chinese to begin withdrawing from Shanghai. Luodian isn't anywhere near these strategically important targets, and yet it saw some of the heaviest fighting. What strategic targets did Luodian threaten?
• Although it's true that Luodian lies between the coastal landings and important targets like the railway and Shanghai, you can see from the map that many other towns also fit these criteria, yet none of them saw fighting as heavy as Luodian. Why weren't other towns between the coast and Shanghai fought as fiercely as Luodian?
• Luodian is indefensible. No defensive works were present due to the previous cease fire, and as a small town on an alluvial plain, defenders were forced to rely on trenches, which could not be dug deep as the water table was so high the soldiers were submerged in the trenches, leaving them vulnerable to bombardment.

So I can't see why Luodian was so important, given its poor (apparent) strategic value and defensibility. And yet both sides considered it important and fought hard for it:

• 300,000 Chinese and 100,000 Japanese troops were involved in Luodian. These numbers are more than a third of the total troop numbers in the whole battle.
• Alexander von Falkenhausen, Chiang Kai-shek's advisor, insisted on holding it at all costs.
• The Chinese suffered a 50% casualty rate in Luodian. The intensity of the fighting earned it the nickname "grinding mill of flesh and blood".

Answer 1

Luodian was a centrally-located transport hub between Shanghai CBD, Baoshan, Songjiang, and Jiading. Holding Luodian was vital to supporting the Chinese position in the whole region. Conversely, losing Luodian seriously threatened to undermine the whole front, since Japanese forces could strike at the heart of the Chinese forces via the roads from Luodian.

In addition, Luodian was squarely on the path to the Shanghai-Nanking Railway. If the Imperial Japanese Army took Luodian, this vital rail link would have been directly exposed. The National Revolutionary Army fighting in Shanghai would be at risk of being cut off and encircled.

For these reasons, Chinese forces hunkered down to defended the countryside surrounding Luodian even after the town was lost. However, the numbers you cited strikes me as a high overestimate; unless it included other Japanese units fighting in the region, in an effort to link up with Luodian and thus outflank the Chinese position in Shanghai.

Answer 2

I found a somewhat better map, showing the major roads leading out of Luodian:

Here you can clearly see that Luodian is a transportation hub; it is at the crossroad of two roads: Jiading-Baoshan, and Liuhe-Dachang. The key point is that this crossroad straddled the entire northern beachfront. The Japanese had made landings at multiple locations from Liuhe to Baoshan; taking Luodian would mean they can easily consolidate their landing forces there by using the roads leading from the coast. In this sense Luodian is somewhat analogous to Caen or Saint-Lô in the Battle of Normandy. It was also important to the Chinese as they can use the roads to transfer troops between Luodian, mainland reinforcements via Jiading, and downtown Shanghai via Dachang, forming a defensive line that protected the all-important Jinghu railway.

Jiading, one end of the crossroads, was a large town that stood between Luodian and the railway. Even more important was Dachang, and after Luodian was taken, the Japanese followed the road to Dachang, but not before heavy fighting on the Yunzaobin River, which ran between Luodian and Dachang.

Wikipedia mentions several locales that Luodian connects. Without qualification, some of these seem redundant:

• Baoshan: true, although it was merely one of several beachheads
• downtown Shanghai: also true, although to get to downtown Shanghai from Luodian, one would have to capture Dachang first
• Jiading: also true, but its importance relied on the fact that it was connected to Luodian, not the other way around, as Luodian was the linchpin
• Songjiang: not sure why this was included; Songjiang is well south of the railway, and to travel from Luodian to it, one would pass many much more important targets like the railway, Shanghai itself, or Hongqiao (airfield).
• and several other towns with highways: unless there are other roads I'm not aware of, I'm assuming this means the towns that lie along the roads, which is a bit redundant because we've covered the much more important endpoints of those highways

Answer 3

From page 99 of Shanghai 1937: Stalingrad on the Yangtze (Peter Harmsen, 2013):

Possession of Luodian would mean control of part of the road south to the town of Dachang and, a little further along the same road, Shanghai proper. Luodian also straddled the road to Jiading, a major town five miles to the west, which in turn was the gateway to the city of Nanxiang, close to the strategically vital railway line connecting Nanjing and Shanghai.

The German General Falkenhausen certainly knew his shit. He foresaw how the defense of Luodian could in turn defend the larger more important cities by slowing the movement of the Japanese. Similar to the Civil War like @T.E.D. mentioned, little towns can be sites of huge strategic logistical importance if they are situated near a mobilization resource, in this instance strategically important roads.