The European/EU eastern border is far too thinly defended. At the present time a Russian invasion force can bypass, surround and defeat the presently available defence forces in several sectors.
However, the Ukrainian reforms during the last four years may help if intelligently and brutally applied to all defence forces in all units and in constant extended exercises.
The first many steps relate to the front-line defence forces.
As the Germans in 1916, the Ukrainians have learned that field fortifications (and supporting obstacles) must be extensive and to save soldiers the front line should only be thinly occupied.
Deep surveillance and attrition of attacking Russian forces must be ensured by the availability og constant employment of masses of different types of surveillance and loitering attack (suicide) drones. Own forces should be protected by various types of anti-drone weapons.
To reduce losses among front line and rear area troops and add to their defence sectors, land drones should be deployed extensively in both combat and logistic roles (as shown on the Atlantic Council photo)
There should be a reserve system available both for replacing and sustaining front line units and for containing front line breakthroughs.
To deter Russian infrastructure attacks and be able to respond, own strong offensive missile and drone forces should be maintained on various platforms, including some secure ones.