There is a bottleneck in the transmission of information between Luoyang and Shangdang, that is, the Yellow River, and as long as the Yellow River crossing is blocked, all communication links between Luoyang and Shangdang can be cut off.

And there are only a few Yellow River crossings near Luoyang, so Cao Liang can expect that Sima Yi will definitely block the Yellow River crossing before the operation, so that Luoyang can cut off the connection between Luoyang and the Shangdang side, at least Sima Yi thinks so.

In anyone's opinion, this problem must be unsolvable, the army on the Shangdang side must wait for the news from Luoyang to take corresponding action, and it will definitely not work to postpone, the overall situation on the Luoyang side has been decided, and the Shangdang army will kill again, it is obviously too late.

But it's even worse in advance, who knows if there is a rebellion on the Luoyang side, if not, the Shangdang army will be killed under the city of Luoyang, but they are suspected of rebellion.

Sima Yi took a fancy to this, so he blocked the Yellow River crossing before he acted, this is obviously a foolproof plan, as long as any personnel on the Yellow River crossing are cut off, then the news from Luoyang will definitely not reach the Shangdang.

In the army of the upper party, it is impossible to act without the latest directives.

But is it really incomprehensible? Cao Liang smiled slightly, you have a good plan, I have a wall ladder, this living person can still suffocate dead urine?

So Cao Liang deliberately ordered someone to make a relatively large omission. In this era, there were no timekeeping tools such as clocks and watches, but that does not mean that the ancients would not keep time, during the day, people would use watches and sundials to keep time, and at night, they would use missing engravings to keep time.

Missing engraving, a timer invented by ancient Chinese scientists. A drain refers to a pot with a hole, and an engraving refers to a floating arrow with a scale attached. There are two types: drain type and water receiving type. In the early days, most of them were leakage type leakage carvings, water flowed out from the hole of the leaky pot, and the floating arrows in the leaky pot fell with the water surface, and the scale on the floating arrows indicated the time. The floating arrow engraved in the water receiving bottle indicates the time with the rise of the water surface, and a multi-stage water receiving bottle can be placed in order to obtain a uniform water flow.

It is impossible to study when the missing engraving occurred, and by the time of the Three Kingdoms era, the missing engraving had developed to a very precise point, and the time error was already very small.

However, most of the missing engravings, the range of the time is usually one day and night, that is, twelve hours, Cao Liang specially asked someone to make a thirty-six hours of missing engraving, that is to say, the water in the missing engraving, all dripping, it takes three days and three nights.

When this missing moment was sent to the Gaodu of Shangdang, Yanghu and Deng Ai Shibao were staring at each other, not understanding Cao Liang's intentions.

Missing engraving can be said to be a relatively common thing, it is rare to see it in the homes of ordinary people, but for the army or the world's wealthy families, this thing is too common, and it is often available in the state army.

It's just that this missing engraving seems to be much more than the ordinary missing engraving, this volume is almost three times that of the ordinary missing engraving, Cao Liang specially sent this thing from Luoyang, it should be some special use, but the three of them looked around for a long time, and they couldn't figure out Cao Liang's intentions.

The messenger handed Cao Liang's letter to them, and after the three of them read it, they suddenly realized.

It turned out that this three-day leak was specially prepared by Cao Liang for this operation, and after this leak was activated, Cao Liang would send people to report from time to time, and whenever the messenger arrived, the water in the leak would be filled up immediately, and the timer would start again, until all the water in the leak was dripped, and no new messenger arrived, and that was when the state army attacked.

Cao Liang's arrangement is actually a negative timekeeping method, limited to three days, if the Shangdang side can't receive the news from Luoyang, then Deng Ai and they don't need to wait any longer, and immediately send troops to attack Luoyang.

Under normal circumstances, Cao Liang would send a messenger to Shangdang at any time within three days, and the letters brought by the messengers sometimes had specific contents, and Cao Liang would send them the latest orders, and sometimes they would be blank letters, and they only needed to restart the countdown.

Under normal circumstances, the state army assembled in the high capital of Shangdang needs Cao Liang's order to send troops, but if the Yellow River crossing is blocked, Cao Liang's order to send troops is likely to be blocked, and it cannot be conveyed to Shangdang, and Shangdang's army will not be able to send troops.

But with the negative timing method, the situation will be the opposite, after receiving the news within the three-day deadline, the state army will suspend the operation, and if the news is not obtained within the time limit, it will send troops.

In this way, Sima Yi's blockade of the Yellow River crossing would become meaningless, and the state army would be delayed for about two days at most, and with the speed of the cavalry march, these two days would be negligible.

Previously, Deng Ai and the others were also racking their brains to find a way to solve this communication problem, because they couldn't get the news from Luoyang, they didn't dare to act easily anyway. If it is a good place in the Pingchuan area, there are thousands of roads, and you can always bypass the enemy's blockade.

However, crossing the Yellow River is a huge problem, no one has wings to fly over it, and if this bottleneck problem is not solved, the communication between Luoyang and Shangdang is a big problem.

Deng Ai and the others almost focused on how to break through the blockade of the Yellow River, but they didn't expect Cao Liang to find another way and solve this problem easily.

How much brains does it take to think of this way? Deng Ai and the three of them are admired by the five-body casting.

Now, things seem to be simpler, but with it comes the pressure, and once the leak is activated, no one knows when it will leak the last drop of water inside.

Every time the messenger came, the water in the leaky moment would be filled, and the countdown would start again, and as the water in the leaky moment continued to decrease, Deng Ai's spirits also became tense.

This process of repetition is indeed a test of the human spirit, as soon as the messenger comes, their nervousness will become relaxed, and as the water in the leak continues to decrease, their spirit will become tense again, and no one can tell whether the messenger's arrival is disappointing or hopeful.

However, for the Bingzhou army, they have made all preparations to send troops, and the vast majority of the troops of the Viet Cavalry Battalion, the Tun Cavalry Battalion and the Infantry Battalion have been deployed to Shangdang Gaodu, which is adjacent to Hanoi County, and all they have to do now is to quietly wait for the moment when the water in the leak is exhausted.