Ukraine has been at war with Russia for more than two years and recently winds have

been hard to come by.

Here's our colleague James Marson.

The Russians using their greater size

have been able to advance slowly, methodically, with great losses, but still to inch forward, particularly

in the east of the country.

But despite having a smaller Navy, the Ukrainian military has found an effective strategy at sea.

Their key, naval drones or sea drones, a kind of unmanned boat about the length of an SUV.

Tonight Ukraine appears to be ramping up its offensive.

A sea drone targeting a Russian warship.

Sea drones attacking and the Ukrainians say sinking a Russian warship inside

occupied Crimea.

Naval drones are small boats which are controlled by remote control so they don't have an on board

crew they can be steered from a distance they're gray they're small they hang about between the waves, so they're much harder to detect.

These drones are part of Ukraine's strategy to make gains against a much larger and better equipped enemy.

So what Ukraine has done is find cheap, easy to produce, and effective small weapons that can in a way negate that Russian

advantage, the advantage of size by being cheap,

nimble, easy to use and effective.

Right, they've had to innovate essentially

because they can't just meet them toe-to-toe. Right, they can't go meet them toe to toe.

Right, they can't go toe to toe,

so they've had to innovate.

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