The "landmine" called a caltrop is an area denial weapon made up of two or more sharp nails or spines arranged in such a manner that one of them always points upward from a stable base. Historically, caltrops were part of defenses that served to slow the advance of troops, especially horses, chariots, and war elephants and were particularly effective against the soft feet of camels.
In Roman Republic warfare the caltrop was being used against enemy war elephants as early as 279BC in the Battle of Asculum.
Archaeological excavations around Alesia show the use of caltrops by Caesar's legions.
A Roman historian mentions their use against Persian cavalry in the 5th century.
In the 6th century the Roman historian Procopius tells how the general Belisarius used caltrops to defend open gates during the siege of Rome.
As cavalry rose in importance the use of caltrops gained in importance to hamper an enemy cavalry attack or to restrict movement.
In an anonymous 6th century Roman treatise caltrops are presented as a full-fledged war stratagem.
He said the caltrops should be used to protect the Roman fortified camp. The caltrops would be laid along the ditch some 12.5 meters in length. The commander of each unit would be responsible to gather them for their re-use and to prevent them from injuring their own troops when they leave camp.
Rear guard soldiers were told to have a supply of caltrops available to delay or wound any enemy in pursuit.
In the Emperor Maurice's war manual the Strategikon, the caltrop is also shown to protect the camp as well as for use on the battlefield. A light wagon was assigned to Roman units with "caltrops tied together with light cords attached to an iron peg so they can be easily collected." If attacked from the rear the caltrops can be thrown from the wagon into the path of an enemy.
When part of the army is forced to leave the main force they are told to bring caltrops along.
Maurice called for a "minefield of calthrops" on the battlefield. Unobserved by the enemy, Roman troops were to spread calthrops along the entire field of battle 100 feet deep. In four or five places there would be 300 foot wide gaps that would allow Roman troops to go and return unhurt. These passages would be market with tree branches or piles of stone. If an enemy was enticed into this minefield they would be confused and more easily destroyed.
The Taktika of Emperor Leo VI written in the 9th and 10th centuries reaffirms the use of calthrops. Almost word for word Leo repeats Maurice's writings on calthrop use in camps or the battlefield.
Leo is original in urging calthrops be thrown on to the decks of enemy ships to hamper the movement of the crews.
In the 10th century work by Heron of Byzantium he suggested wooden soled shoes to protect the infantry and farm rakes to clear a path of calthrops.
In 1082 Emperor Alexios Komnenos used fields of calthrops against Norman cavalry in the Balkans - - - - but the Normans avoided the calthrops by flanking the Roman line.
But nothing lasts forever.
At the end the Empire's population was exhausted, their wealth was spent, their economy was shattered and perhaps worst of all they were mostly alienated from Western Europe who had come to their aid in the previous centuries.
A few competent rulers in a row would have helped them more than caltrops or maybe just a few competent diplomats.