Ukraine has a key bridge in its sights, and Russia is throwing whatever it can, from sunken ships to smoke screens, into trying to defend it

• Russia has set up a number of defenses to protect the Kerch Bridge from Ukrainian drone boat attacks.
• The protective measures include using smoke screens, sunken ships, and containment booms, intelligence indicates.
• The Kerch Bridge is a key supply and logistics line and a symbol of its influence over Crimea.

Ukraine has twice targeted a key bridge connecting the Russian mainland to occupied Crimea, damaging the important structure both times, and now Russian forces are scrambling to up their defenses, seemingly throwing whatever they can at the problem.

The new defensive strategies for protecting the Kerch Bridge include purposefully sunken ships, smoke generators, and containment booms, among other things, according to Western intelligence. The random assortment of efforts are apparently there to prevent unmanned surface vessels (USVs) from reaching the bridge, a key target for Ukrainian forces that was most recently damaged by a USV in late July. 

But it's unclear how effective the defenses will be or how they'll work together as a network to protect the vulnerable 12-mile-long bridge. 

Earlier this week, satellite imagery surfaced showing a peculiar Russian attempt to defend the Kerch Bridge: a barrier of sunken ferries intended to make it harder for drone boats to navigate in the water.

The six sunken ships are separated by what Western intelligence said is about 160 meters, or around 525 feet. The ships only guard a fraction of the bridge, and the distance between them leaves plenty of space for smaller waterborne drones around the size of jet-skis to pass through.

In addition to the sunken ships, Russia has also employed defenses like smoke generators, presumably to make targeting more difficult, though the effectiveness of this as a defense is questionable. Wind and weather can limit the effects of any kind of smoke screen, and the Kerch Bridge is also a stationary target with a known location.

Other Russian defensive measures include air defenses, possibly to combat aerial drones or cruise missiles, and containment booms — floating barriers typically used to contain oil spills that could potentially hinder USV operations but might, as experts have said previously, be vulnerable to multiple drone strikes in rapid succession.

The spread of defenses being used speaks to both the importance of the Kerch Bridge and Kerch Strait to Russia, as well as the difficulty countering the threat posed by Ukraine's drone boats.

Russia relies on the bridge — which was completed in 2018 — for convenient access to Crimea. It's been used as a supply and logistics line for the military, and it gives Russia improved cultural and economic control of the peninsula.

The bridge is also a symbol of what is seen as Russian President Vladimir Putin's crowning achievement — his illegal annexation of Crimea in 2014. That has made the Kerch Bridge a symbol of Russian oppression of Ukraine and a key target for Ukrainian forces.

Outside of the Kerch Straight, Ukraine's USVs have carried out many recent attacks across the Black Sea, wreaking havoc on Russia's naval forces. In one case, a drone boat was able to approach a warship seemingly undetected and cause what appeared to be severe damage and flooding.

The drone may not have been spotted — the sleek, black USVs are difficult to see in the water — but Ukraine's ability to hit larger Russian military assets with its comparatively cheaper drone beats and the lack of a Russian response hints at a Russian force protection issue, long a problem for the Russian military.