Russian defense lines during the Russian invasion of Ukraine
Russia has built numerous defense lines in Ukraine during its invasion. Surovikin Line 

The Surovikin Line is a complex set of fortifications in southeastern Ukraine, engineered by and named for Russian general Sergey Surovikin. Surovikin had the line built during his tenure as the overall theater commander immediately after Ukraine's 2022 Kharkiv counteroffensive. The Kyiv Independent published on 24 March 2023 an interview of a man called Bohdan from an undisclosed town in southeastern Zaporizhzhia Oblast who claimed to have been held captive by Russian soldiers in a checkpoint outside Vasylivka and forced to dig trenches for them. Bohdan claimed to have been held for four months; during that time, he had been considered to be missing by his relatives. After that, he was brought to Melitopol where he was set free. At the time of the publication his interview, he was remaining in Russian-occupied territory. According to Bohdan, Russian soldiers kept many other Ukrainian civilians captive there for digging trenches and "other hard work". Dmytro Orlov, the exiled mayor of Russian-occupied Enerhodar, claims that as of 17 February of that year, 200 Ukrainian civilians were being held as prisoners in an area between Vasylivka and Kamianske for these purposes. Wagner Line 
The Wagner Line (, )  is a defense line built in eastern Ukraine by the Wagner paramilitary group during the Russo-Ukrainian War. Overview 
On , Yevgeny Prigozhin, the leader of the paramilitary group Wagner, announced that he had begun the construction of a defense line. The aim is to prevent Ukrainian troops from advancing towards the Luhansk region in eastern Ukraine, which was annexed by Russia in . According to the Russian media, it is a "second line of defence in case the Ukrainian armed forces try to penetrate the area. In a report dated , the British Ministry of Defence considered that Moscow prioritized the construction of defensive positions on the Svatove–Kreminna line. Structure 
The line consists of two double rows of pyramidal concrete blocks called "dragon's teeth" to block tanks from advancing. Between these two defensive curtains, a deep trench and firing stations complete the device. It is not known whether the line has mines. The project foresees about  of fortifications in eastern Ukraine, up to the Russian border. The line shall extend on a south-north axis starting from the city of Svitlodarsk, along the front line to the Donets River, and then form an acute angle again eastwards, following the course of the river to the border. Andrey Bogatov, another leader of the Wagner Group, said that construction of the line had also begun in Belgorod Oblast, Russia. Efficiency 
Several experts questioned the efficiency of the line. For Xavier Tytelman, a conflict observer and defence consultant, "The dragon's teeth should be partially buried so that only the tip can pass through. A simple armoured bulldozer is enough to turn them over". According to the Ukrainian Governor of Luhansk Region, Sergey Gaidai, only 2 km have been built to date. The ABC News considers -through the study of satellite photos - that 12 km have been built. According to the ISW, Prigozhin's proposed extension of the Wagner Line is intended to defend the border between Belgorod Oblast and the Ukrainian oblasts of Sumy, Kharkiv and Luhansk, but "would not cover the northern part of Luhansk Oblast up to the line of contact with the occupied territories, thus contradicting the Kremlin's promises to defend the entire Luhansk region". Dragon teeth are not buried or camouflaged, which, according to a BBC article, severely limits their effectiveness. It may also be noted that the line does not protect the city of Sievierodonetsk. The local authorities in Belgorod have already asked the Wagner Group to stop the construction of the trenches. Defense line in Crimea

Defense line on the Russia–Ukraine border

Khrenin Line 

The "Khrenin Line", named for Belarusian Defense Minister Viktor Khrenin is located near Homel in Belarus,  from the Belarus–Ukraine border. It is about  in total, and includes dragon's teeth anti-tank barriers and trenches. See also
Russia–Ukraine barrier, attempt by Ukrainian government to build a defense line prior to 2022
Panther–Wotan line, built by Nazi Germany in the region during the Second World War

References 

21st-century fortifications
Defense lines