You can design from a small lego like pool own jets,tanks, sams,helicopters,ships and submarines and depending on how much you fund R&D in armor,firepower,missile technology etc the specifics will upgrade over time faster or slower.
You can make false flag operations or embargoo countries and destabilize them, but it doesn't work well if you are the only country who is sanctioning countries, you can take assassinations on politicians or just simple civilians as a flase flag, chances are still high that you get captured and relations fall if you are a weak country will encourage war if you are strong not much will happen.
Here some pics.
This is total nuclear response you can do it anytime but anyone that is attack by nukes will retaliate with almost 100% arsenal, but you can make alliances with countries and let them build ABMs like NATO does right now.
Here some military vehicles, you can either buy off from the world market which are mostly old or build new or even ask countries to build for you but you need good relations to have that option, you can also sell your equipment but most of the time no one will buy.
You can also invest in domestic market to run up specific production goods but it is somekind buggy or not well calculated because it will ruine you if you do it several times in short time for same products, you can also lower taxes on import and export that will piss off some countries and you make money.
You can annex countries, if you have big warships or nukes you can target to attack military targets or civilian population, you can try to wipe out nations but nuking small countries with 1000 nukes will not kill entire population it reduces after few nukes only some small portion of the population, but very effective against military.
You can form off alliances, you can pay debts of other countries to better singnificantly the relations if you want to farm alliance, declaring war out of nowhere always worsens relations with all countries, so you need a well planned and successful false flag operations.
I recommend it because it has more things to it than DEFCON.