Ukraine Destroys Road And Rail Bridges To Cut Russian Supply Lines

Bigger Bombs For Busting Bridges

Ukraine’s problem has always been lack of powerful enough weapons. Attempted strikes using salvoes of HiMARS missiles failed to destroy a bridge in the Kherson region in 2022 and Storm Shadow missiles only caused minor damage to the Chonhar Road Bridge in 2023. Both were re-opened after a few days. In both cases the weapons only damaged the road surface, but to really put a bridge out of action means destroying the concrete or steel supports holding up the road or railway.

This has always been a major challenge. A U.S. study in WWII found that on average it took 190 sorties by medium bombers dropping 350 tons of bombs to destroy one bridge. This was due to the difficulty of hitting the supports. Improved accuracy made a big difference: “If bombing accuracy could be Improved to something approaching training school accuracy….The number of sorties required would be reduced from 190 to 33.”

Achieving such accuracy was impossible in practice. British engineering genius Barnes Wallace came up with a different idea: giant earthquake bombs. Rather than needing a direct hit on a support, the bomb could land nearby, where it penetrated deep underground, setting up shockwaves which would destroy the bridge. Wallace’s 22,000-pound Gland Slam bombs were first used to put the Bielefield railways viaducts out of action in March 1945.

Outsize bombs were rarely practical and the bridge problem continued during the Vietnam War. The notorious Thanh Hoa bridge resisted many attempts to destroy it, including a 1965 raid by 30 F-105D Thunderchiefs dropping eight 750-pound bombs apiece. The bridge was eventually destroyed by a new invention: 2,000-pound Paveway laser guided bombs able to precisely target the concrete supports. Even then it took 26 bombs to finally close the bridge.

The conventional wisdom is that downing a major bridge requires plenty of large precision munitions. Ukraine has always lacked the air superiority needed to deliver such attacks. But with the drone revolution, things have changed,

Drones Versus Bridges

Ukraine’s weapon of choice for this appears to be the Fire Point FP-2 attack drone. Evidence includes debris found at attack sites, and comments on social media by Fire Point executives claiming the strikes.

The FP-2 is a modified version of the long-range FP-1, with fuel tankage exchanged for a bigger warhead. The range is cut from around 1,000 miles to around 120, but the hitting power is more than trebled from 110 pounds of high explosive to 350.

Crucially, the FP-2 has precision guidance, with the operator guiding it in like an FPV attack drone.

350 pounds is a small warhead by the standards of the Paveway series, but what Fire Point brings to the party is numbers. The FP-2 costs a reported $55k and Fire Point makes hundreds every day. As it does not need an aircraft to carry it, any number can be launched with no risk to a human pilot.

In sense what we are seeing is a large-scale version of the attack using dozens of small FPV drones to bring down a two-lane road bridge seen last month. By progressively chipping away at the supports, they can bring down the entire structure.

This bit-by-bit approach means that each drone is directed to exactly the right spot to continue the damage caused by the previous one. The process can be continued over several days, which may bring other advantages.

On the night of June 22^nd, Ukrainian drones hit the railway bridge over the North Crimean Canal, near the village of Rozdolne, leaving it partially destroyed. The next day members of a local resistance group reported that special railway repair equipment had arrived, and that night the drones struck again, destroying the repair equipment and collapsing the remains of the bridge.

This “double tap” approach not only downed the bridge, it also deprived the Russians of essential repair equipment to recover from future strikes.

The double road bridge at Hranitne was reportedly attacked by 20 FP-2 drones which successively brought down supports until both roadways gave way. However Fire Point chief designer Denys Shtilierman posted an image of the attack with the comment “3 FP-2”. This discrepancy may be because the attack also involved decoy drones, and the Russians may have exaggerated the number of drones to make the defensive failure more excusable.

Ruta: Deadly Drone Missile Hybrid

Watling says that another weapon has hit some of the bridges. This is Ruta, which Watling classes as a cruise missile rather than a drone, although it is sometimes referred to as a “missile drone.”

The dividing line between drones and cruise missiles is blurred and the distinction is an arbitrary one. While most drones are propeller-driven, some have jet engines, and some, like the Russian Shahed, some in both propeller and jet-powered versioned.

The Ruta series, made by Netherlands-based Destinus are mini cruise missiles (or missile drones), less than a quarter the size of the U.S. Tomahawk. The Block 2, designed for “extended-range precision strike against hardened and high-value military targets” carries a 500-pound warhead and has a range of more than 400 miles. The estimated cost is around $400k, but the speed of around 600 mph makes this much harder to intercept or shoot down than the 125-mph FP-2.

What is impressive is that flying at low altitude and high speed, the Ruta is still accurate enough to hit bridge supports. This would be virtually impossible with for human reflexes, but Ruta has a camera (daylight and thermal) with AI-based target recognition of defined targets​.This suggests the vision system is fast enough to lock on to and hit a bridge support.

The logistics-lockdown bridge-busting drive is hitting its stride. Russian air defenses have been severely eroded, there are reported shortages of missiles, and some systems are being pulled back to defend Moscow. With production lines turning out large numbers of FP-2s, and some 700 Rutas on order, the next few months could be interesting.

Russian lines of supply may get cut in many places, leaving forces without fuel or ammunition and putting severe strain on the entire region of occupied Crimea. Military planners in the rest of the world may also want to pay attention when this is happening in an area where Russian has, in theory at least, complete air superiority.